#67 streamswitcher

[CodeCasterNL]

@robvdpol worth a look (when done, fixes #67)? It currently looks like this:

Still a couple of issues:

• No loading spinner while switching, looks like stream hangs.
• Focus required on player.
• Sound's gone after a few switches.
• Hotkeys not shown in context menu.
• I'm not entirely sure this is thread/async safe all the way.
• The settings format and its possible values are undocumented yet.
• There's no UI to edit the keybindings.
• The PlayerControl.TogglePlayPause shortcut (Ctrl+P), included for demonstration purposes, still needs to be bound.

It now generates default keybindings upon startup when not found, which are saved on exit, and in an open player window you can (first click the player) and then press the hotkey you want. Hardcoded (but configurable after first run) keys for now:

• Ctrl+F1: World Feed
• Shift+F1: VER onboard
• Shift+F2: HAM onboard
• Shift+F3: BOT onboard
• Ctrl+F2, F3, F4: graphs/timings/tracker
• And more.