Make Elisa aware of users' video folder hierarchy

It should be possible to provide Elisa with a folder hierarchy a user has his/hers videos stored. As videos don't often have metadata stored, we can't rely on that and the filename itself is often not enough.

The user should provide a hierarchy string, something along the lines of:

'%Show%/S%Series%/%Episode%. %Title%' for TV shows and

'%Year%/%Title%/%Filename%' for movies.

Based on that searches made by the media scanner could get much more reliable.