Video info scanner refactoring

[tamland]

This is an attempt at untangling this spaghetti. Scanning movie folders vs tv folders hardly have anything in common at this point, making it impossible to follow. Please see individual commits for step-by-step.

If I have done this correctly, there should be no bug fixes or behavior changes in these commits.

[mkortstiege]

Finally. Looks fine from a brief look. I´ll check in detail, run some tests and report back.

[Montellese]

Any refactor in this area is very much welcome. I'm not very knowledgeable in this code though so I don't feel comfortable commenting on the "unreachable" code that has been removed. Some of it simply becomes unreachable due to the changes made in this PR and I can't judge if these changes are alright or not.

[tamland]

@Montellese I tried to do this very incremental so it would be possible to follow. The first two commits just copy-paste DoScan, then the tv part of movie scan, and vice versa, is removed. The 'unreachable' part is because of the content checks.

[MartijnKaijser]

@tamland @mkortstiege would be nice if we could get this cleanup soon so we can have wide testing for regressions.

[tamland]

Too much conflict. Will rather redo if we don't come up with something better;)