Use libtorrent instead of MonoTorrent.

Features broken:

- Magnet links

- Network interface binding

- Encryption type setting

- Torrents Events

- Peer list

- Add peer manually

- Delete data when removing torrent

- Individual torrent settings

- Hash fail count

- Webseeds tab

- Tracker generic state (working, offline)
- Tracker UpdateIn timer
- Tracker PeersCount

- .NET v4 support

Still need todo:

- Torrent state saving (well it's partially done)
- A LOT of polishing here and there
- Modify Ragnar wrapper to provide the IsValid property (and other important properties)