Bug 844347: separate Sync-specific from common pieces in {SyncConstants,GlobalConstants}.java.in.
Bug 844347: fold BackgroundConstants.java into GlobalConstants.java.in.
Bug 844347: move org.mozilla.gecko.sync.GlobalConstants to org.mozilla.gecko.background.common.GlobalConstants.
Bug 844347: move Logger and log writers to org.mozilla.gecko.background.common.log package.