GUI - Better support for keyboard input

[historic_bruno]

It would be nice if the engine GUI would handle more standard keyboard input:

• Pressing enter when a button has focus should cause an onPress event

• Tab switching of focus between controls - the ordering could be the same as in the page XML, left to right for children of a given parent object, and/or support a "taborder" property to override the defaults. Obviously not every control should be included in the tabbing, restricting to input controls seems reasonable.

• Support keyboard accelerators, which are usually specified with an ampersand (&) character in the caption of an input control (the corresponding accelerator is often underlined). This way a dialog that asks "&Yes"/"&No" could be answered with the Y or N keys.