Texture Browser Form: some minor logic fixes (no texture groups were selected...

Texture Browser Form: some minor logic fixes (no texture groups were selected when initial texture was empty and no texture group was stored in the program configuration).
Texture Browser Form: don't save current texture group when the form was canceled.
Keyboard Shortcut Reference export: generated html will now be saved to program configuration folder if working folder is write-protected.
Internal: added SupportedMapFormats property to EditModeAttribute. A mode with this property specified will be available only in specified map formats.
Interface: Ceiling Align Mode and Floor Align Mode are now enabled by default.
Interface: Ceiling Align Mode and Floor Align Mode are now only available in UDMF map format.
Interface: Visplane Explorer Mode is now available only in Doom map format.