Reduces visibility of internal fields/methods

Reduces the visibility of all fields to private and create setters/getters
when necessary. Exceptions are fields with GuiSync as these need to be
public.

Reduces the visibility of internal methods to private/protected/default when possible.

src/main/java/appeng/container/guisync/GuiSync.java

@@ -19,11 +19,18 @@
 package appeng.container.guisync;
 
 
+import java.lang.annotation.ElementType;
 import java.lang.annotation.Retention;
 import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
 
 
+/**
+ * Annotates that this field should be synchronized between the server and client.
+ * Requires the field to be public.
+ */
 @Retention( RetentionPolicy.RUNTIME )
+@Target( ElementType.FIELD )
 public @interface GuiSync
 {