Add server connection "library" feature

[avojak]

Currently the app is WYSIWYG (what you see is what you get), meaning that all stored connections are shown in the side panel. If it's not there, we don't know about it. However not all connections shown need to be active (disconnected servers can still be known and shown/saved).

An option would be to have a "library" of sorts with saved connection information. This might cut down on potential clutter if there are lots of connected servers. This could allow setting some connections as hidden when disconnected, etc.

This would also add a fair bit of complexity and wouldn't be quite as intuitive. Currently I'm a fan of the WYSIWYG approach because it's more obvious to a user. Looking for some feedback on this though.