Use API and allow web interface

This pull request adds usage of Btsyncs API to add and remove shared folders. It also makes it possible to enable the web interface (although it doesn't detect removed folders through the webui which is kind of an issue, but only for those that does that). Hopefully this resolves #1.

(This is missing some nice formatting of the up/download speed though.)

To build it create you need to add the file openmediavault-btsync.key in /var/lib/openmediavault with the contents like this:
```
# This key belongs to OpenMediaVault Plugin Developers. 
# If you want to build your own application, please do not use this key.
# Instead request a key at http://www.bittorrent.com/sync/developers
LONGAPIKEY

```