Fixed: Use Nzb title as scene name when available

- Use Nzb title as scene name when available
- Only use file name as scene name when its highly likely that it's an actual scene name
- Don't store `DRONE` as default release group in the DB
- Clean up the db removing obviously wrong scene names


For example Continuum season 3. (nfo: http://www.usenet-crawler.com/search/continuum%20720p%20web-dl?index=3)

Would be an interesting debate to determine what's scene or not. There are plenty of examples of 'releasegroups' that aren't scene groups, such as -BTN.
You can draw an arbitrary line about what's scene or not, inevitably someone will cross it.
I simply wouldn't use the absence of a releasegroup to be an indication on whether it's scene or not.

An idea though, what if you take the filename and nzb name, remove separators from both (space, dot etc) then do a fileName.LevenstheinDistance(nzbName). If they are almost the same, use the filename. otherwise use the nzbname.
This should filter out nzbNames that differ by things like spaces.
not really related this this IsScenetitle method though.