Correct some comments
Use String.startsWith(), if available
Fix uninstaller: initialize PrefUtils to correctly work with cache
Testcase:
var backupsDir = handyClicksSets.backupsDir; // "sets.backupsDir" will be cached here
handyClicksSets.backupsDir = "..."; // We don't update cache here and use observer notifications
Initialize uninstaller only after first window will be opened
Improve hasPrefix() usage in handyClicksWinUtils:
always use handyClicksUtils.hasPrefix() and partially restore "ut" shortcut, if loaded from XPCOM component