fixed: the list of actions was not showing up in the preferences window (due to a superfluous parameter in a function)
removed a tip do not providing useful information
made small change in the isDisabled function for the undoCloseTab action
rewrote duplicateWindow action and changed its behaviour so that it now duplicates each tab (instead of just opening the currently open URLs)
made copyImage and saveImageAs actions disableable
fixed the isDisabled condition for the copyImageLocation action