Fixes #1932: Better VersionChecker exception handling

ModVersionFetcher will now return a MissingVersion in case of an exception
instead of letting it propagate upwards.

Also added a generic try/catch to the VersionChecker itself, just in case
any unchecked exception might be triggered inside the thread and at least
not logged correctly.

src/main/java/appeng/services/version/DefaultVersion.java

@@ -1,7 +1,28 @@
+/*
+ * This file is part of Applied Energistics 2.
+ * Copyright (c) 2013 - 2015, AlgorithmX2, All rights reserved.
+ *
+ * Applied Energistics 2 is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * Applied Energistics 2 is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with Applied Energistics 2.  If not, see <http://www.gnu.org/licenses/lgpl>.
+ */
 
 package appeng.services.version;
 
 
+import javax.annotation.Nonnegative;
+import javax.annotation.Nonnull;
+
+
 /**
  * AE prints version like rv2-beta-8
  * GitHub prints version like rv2.beta.8
@@ -13,7 +34,7 @@ public final class DefaultVersion extends BaseVersion
 	 * @param channel either alpha, beta or release
 	 * @param build natural number
 	 */
-	public DefaultVersion( final int revision, final Channel channel, final int build )
+	public DefaultVersion( @Nonnegative final int revision, @Nonnull final Channel channel, @Nonnegative final int build )
 	{
 		super( revision, channel, build );
 	}