only bind tile-keys (space and enter) if they would do some action

this means more KeyBinding for this Hotkeys and more often removing Hotkeys,
but keeps gTile from grabbing them away from focused application all the time
fix autoclosing and also change all occurrences of "this.preferences" to
"preferences"

"this" can only be used out of class-scope where it references to gTile
to the gTile instance itself. using "preferences" is more constistent