Added three functions and a hook for F4 menu modifying.
GM:addF4MenuTab(name, ctrl, icon) add a tab to the F4 menu
GM:switchTabOrder(from, to) switch the order of two tabs
GM:removeTab(tabNr) remove a tab from the F4 menu

All three functions are supposed to be run in the F4MenuTabs hook.

These functions are there until the F4 menu is recoded