Remove from dock

[bilogic]

Is your feature request related to a problem? Please describe.
A XMPP messeger is something I prefer to constantly run in the background, aka shown in the menubar, not in the dock

Describe the solution you'd like
Allow removing from the dock as an option, but retain an icon in the menu (to indicate to the user that beagle-im is running)

Describe alternatives you've considered
None

Additional context
None