[Feature] Display GKey Mapping (on profile change)

[suabo]

Since it is hart to remember 9 key bindings or even 28 if you use all four profiles it would be nice to have the possibility to show the mapping loaded from config. Therefore the config need to get a new field inside of gkeys with a description. The field can be optional to make old config files compatible.

...
"notification_type": "<notify|gkeys>",
...
"g<no_of_gkey>": {
    "hotkey_type": <type of command "nothing" or "typeout" or "shortcut" or "run">,
    "do": "<thing to do>",
    "description": "<description>" (optional)
}

I'll make an option inside the config to show the mapping instead of a notification on profile change.
It would also great to allow binding this method to an gkey. I think it should be possible with the use of the python feature without the need of an extra hotkey_type.

I think it is done quick.