Fix behaviour when kbswitch2 was already running.

It would tell the helpers to quit, and then keep running.
Allow settings to be changed from command line while running.

Works, but code might need a quick once over...
Give kbswitch2 its own documentation.
Merge all kbswitch2 windows messages into 1, distinguished by wParam.

Greedy to use two, as there's only so many global user messages
available...
Add batch file that quickly restarts Explorer.

Handy when kbswitch2 gets its hooks into it.
Add note about AutoHotkey to kbswitch2 documentation.
Add latest build of kbswitch2.