CMSSIX-298: Move lock-timeout handling to the client
 - introduced new config property cms.repository.lock.timeout with default value -1
 - expose cms-lock-timeout with constants input-module
 - store lock-start date object in session when lock is created
 - added removeLock function that also invalidates the resource by updating the type property with the current value
 - when a lock is removed by a timeout while the browser is still open, a dialog is displayed informing the user that the lock has been removed. The user can either click cancel and close the document manually, or click OK to reload the cms.
 - removed return statement on onbeforeunload the get rid of alert before reloading top frame
 - implemented expiredLocks check in isUserAuthenticated callback