Fix for 'The "optimized" argument must be followed by a library.' cmake failure

adding simple doc build script

this should fix stylesheet importing on windows, but we'll see

fix of /saveStyleSheet command, error message on stylesheet import fail

tweak and document abstract page

on file save: create parent directories if needed

unbreak command auto-completion (was broken since r0b92341adb6a - 52 commits ago)

chat: + added timestamps (can also be css styled and disabled) + allow exchanging stylesheet by just dragging a *.css file into the chat widget! + /saveStyleSheet command for keeping the applied stylesheet for future runs + /discardStyleSheet to reset to the saved/default stylesheet Note: I noticed command auto-completion is broken, don't know since when. annoying.