Add options for tray icon behavior

[ckaczor]

I'm used to slightly different behavior for applications with a tray icon:

1. Hiding when the window is minimized rather than when it is closed
2. Showing menu with a double click on the tray icon rather than a single click

I added some options to allow this but preserving the current defaults:

• "Hide main window when minimized" - defaults to off
• "Hide main window when closed" - defaults to on
• "Mouse trigger" - default to single click - has option for double click
• "Mouse action" - defaults to "toggle window visibility" - has option for "show window"

The mouse options (trigger/action) are hidden on Linux since there's no double click for the tray icon.

I tested on Windows and Linux but don't have a Mac system to test on.

Thanks!