Use getApplicationContext() instead of getContext() to prevent memory leaks.

Using whatever `Activity` as the `Context` used to construct the first content
provider means that it will be help onto in memory until the application is GC'ed.

F-Droid/src/org/fdroid/fdroid/data/FDroidProvider.java

@@ -86,7 +86,7 @@ public abstract class FDroidProvider extends ContentProvider {
     }
 
     protected final synchronized SQLiteDatabase db() {
-        return getOrCreateDb(getContext()).getWritableDatabase();
+        return getOrCreateDb(getContext().getApplicationContext()).getWritableDatabase();
     }
 
     @Override