Mecahnism to switch to open sessions quickly

[timoc]

There are other suggestions in the trac for this, but i think the easiest would be:

- To have a configuration option for 'fast session switching' (possibly with fast selection key config)

- To look for a 'fast session' keypress after toggle guake button, or after a double press of the toggle guake button, and then a session number, or first character of the session name.

Workflow with sessions (home, work, other) and 'pause' as the toggle key and fast session key:

<pause><pause>h -> switch to session tab home

<pause><pause>2 -> switch to session tab work (or other if session numbering starts at 0)

[Dokan]

 https://github.com/Guake/guake/issues/86