Add multi-window spport

[Antolius]

User should be able to open multiple Starfish windows by either:

1. Right clicking a link on a Gemini page and picking a new "Open link in a new window" option
2. Right clicking the Starfish icon in a dock and picking a "Open a New Window" option
3. Dragging a tab out of an existing window

Each window should persist it's own session states (e.g. history, page loading status, info on certificates etc.).
It should be possible to move tabs across windows, in which case their session state should transition with them.