Change scheduler behaviour with tasks

Previously, a task could only be scheduled once.
Tasks can now be scheduled once for every kind of queue (timed, asap and lazy)
Refactor scheduler into more modular queue classes
Add support for show sources to trigger refreshes
Fix typo in readme
Fix problem where nab would not terminate

Make sure all threads terminate when the main thread terminates, either by daemon threads or by being instructed to stop
Fix automatic response to changes in config files to behave as expected
Fix bug with rescheduling timed events
Fix crash on startup
Remove libtorrent dependency

This dependency is important, but can't find an easy way to get it just yet
Revert accidental conflict commit
Add requirement to setup.py for lxml
Add support for url to image banner for shows
Fix crash when reloading scheduled tasks
Add support to get download progress from plugins
Add gitignore
Make RSS feed plugin not retry if no files found

Most issues with no files found are not fixed by retrying and this only slows down the software.
Change kickass proxy
Make download and video paths case-insensitive

Allows default config file to function regardless of capitalization of these folders or paths
Add swp files to gitignore
Add local service discovery and default DHT router to libtorrent