Fixes #976 Now uses GitHub to retrieve most current version

Reworked whole Version Checker with an extensible interface to add any other service later on easier.
The version checker now has its own config file, to collect the different options and extract them from the main config file.
In that you can specify how fine the versions should be checked.

src/main/java/appeng/services/version/github/DefaultFormattedRelease.java

@@ -0,0 +1,32 @@
+package appeng.services.version.github;
+
+
+import appeng.services.version.Version;
+
+
+/**
+ * Default template when a {@link FormattedRelease} is needed.
+ */
+public final class DefaultFormattedRelease implements FormattedRelease
+{
+	private final Version version;
+	private final String changelog;
+
+	public DefaultFormattedRelease( Version version, String changelog )
+	{
+		this.version = version;
+		this.changelog = changelog;
+	}
+
+	@Override
+	public String changelog()
+	{
+		return this.changelog;
+	}
+
+	@Override
+	public Version version()
+	{
+		return this.version;
+	}
+}

src/main/java/appeng/services/version/github/FormattedRelease.java

@@ -0,0 +1,21 @@
+package appeng.services.version.github;
+
+
+import appeng.services.version.Version;
+
+
+/**
+ * Represents the acquired, processed information through github about a release of Applied Energistics 2
+ */
+public interface FormattedRelease
+{
+	/**
+	 * @return changelog
+	 */
+	String changelog();
+
+	/**
+	 * @return processed version
+	 */
+	Version version();
+}

src/main/java/appeng/services/version/github/MissingFormattedRelease.java

@@ -0,0 +1,37 @@
+package appeng.services.version.github;
+
+
+import appeng.services.version.MissingVersion;
+import appeng.services.version.Version;
+
+
+/**
+ * Exceptional template, when no meaningful {@link FormattedRelease} could be obtained
+ */
+public final class MissingFormattedRelease implements FormattedRelease
+{
+	private final Version version;
+
+	public MissingFormattedRelease()
+	{
+		this.version = new MissingVersion();
+	}
+
+	/**
+	 * @return empty string
+	 */
+	@Override
+	public String changelog()
+	{
+		return "";
+	}
+
+	/**
+	 * @return {@link MissingVersion}
+	 */
+	@Override
+	public Version version()
+	{
+		return this.version;
+	}
+}

src/main/java/appeng/services/version/github/Release.java

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+package appeng.services.version.github;
+
+
+/**
+ * Template class for Gson to write values from the Json Object into an actual class
+ */
+@SuppressWarnings( "ALL" )
+public class Release
+{
+	/**
+	 * name of the tag it is saved
+	 */
+	public String tag_name;
+
+	/**
+	 * Contains the changelog
+	 */
+	public String body;
+}

src/main/java/appeng/services/version/github/ReleaseFetcher.java

@@ -0,0 +1,90 @@
+package appeng.services.version.github;
+
+
+import java.io.IOException;
+import java.lang.reflect.Type;
+import java.net.URL;
+import java.util.List;
+
+import org.apache.commons.io.IOUtils;
+
+import com.google.gson.Gson;
+import com.google.gson.reflect.TypeToken;
+
+import appeng.core.AELog;
+import appeng.services.version.Channel;
+import appeng.services.version.Version;
+import appeng.services.version.VersionCheckerConfig;
+import appeng.services.version.VersionParser;
+
+
+public final class ReleaseFetcher
+{
+	private static final String GITHUB_RELEASES_URL = "https://api.github.com/repos/AppliedEnergistics/Applied-Energistics-2/releases";
+	private static final FormattedRelease EXCEPTIONAL_RELEASE = new MissingFormattedRelease();
+
+	private final VersionCheckerConfig config;
+	private final VersionParser parser;
+
+	public ReleaseFetcher( VersionCheckerConfig config, VersionParser parser )
+	{
+		this.config = config;
+		this.parser = parser;
+	}
+
+	public FormattedRelease get()
+	{
+		final Gson gson = new Gson();
+		final Type type = new ReleasesTypeToken().getType();
+
+		try
+		{
+			final URL releasesURL = new URL( GITHUB_RELEASES_URL );
+			final String rawReleases = this.getRawReleases( releasesURL );
+
+			this.config.updateLastCheck();
+
+			final List<Release> releases = gson.fromJson( rawReleases, type );
+			final FormattedRelease latestFitRelease = this.getLatestFitRelease( releases );
+
+			return latestFitRelease;
+		}
+		catch ( Exception e )
+		{
+			AELog.error( e );
+
+			return EXCEPTIONAL_RELEASE;
+		}
+	}
+
+	private String getRawReleases( URL url ) throws IOException
+	{
+		return IOUtils.toString( url );
+	}
+
+	private FormattedRelease getLatestFitRelease( Iterable<Release> releases )
+	{
+		final String levelInConfig = this.config.level();
+		final Channel level = Channel.valueOf( levelInConfig );
+		final int levelOrdinal = level.ordinal();
+
+		for ( Release release : releases )
+		{
+			final String rawVersion = release.tag_name;
+			final String changelog = release.body;
+
+			final Version version = this.parser.parse( rawVersion );
+
+			if ( version.channel().ordinal() >= levelOrdinal )
+			{
+				return new DefaultFormattedRelease( version, changelog );
+			}
+		}
+
+		return EXCEPTIONAL_RELEASE;
+	}
+
+	private static final class ReleasesTypeToken extends TypeToken<List<Release>>
+	{
+	}
+}