A ton of new features + huge refactor

[ikatson]

New features:

• Torrents can be in multiple states:
  • Initializing / Paused / Live / Error (e.g. out of space on disk or no permissions)
• You can now pause/resume/delete torrent through HTTP API and web UI
• Added armv7 build
• You can now configure "RUST_LOG" through HTTP API

Breaking changes:

• A lot of internal shuffling of things around. If you used the library might need to tweak a thing or two.
• The server that starts with "rqbit download" is now read-only. It also doesn't have persistence. To have a server that allows to upload/pause torrents etc, you need to run "rqbit server start"
• DHT now throttles itself not to send as many requests per second as it used to. This may make things a bit slower. But at least on my Macbook Air it used to lock up system UI (even cursor) because it was sending too many UDP packets in quick succession.