ICE-9605 Factored out useLocalStorage() function that is used in all the places that try to use browser's local storage feature. Modified pushID expiry mechanism to use this function as well.

git-svn-id: http://anonsvn.icesoft.org/repo/icepush/trunk/icepush@38537 1de00972-ac04-4911-a46b-06793c8d78d9