#12 Verify/Update Media Library in background

[Anders Sandvig]

Add functionality to verify and update media library even
when loaded from the cache. What would happen is
something like this:

1) When WinCue is started without a cached Media
Library, the entire library is scanned, researched and
cached.

2) When WinCue is started with a cached Media Library
all files are verified against the cached data and updated
if different.

i.e. one could check the modification time and size of
each file in the cache against the corresponding file on
disk, if either has changed do an update on this file.

3) Any files present in the cache but missing on disk
should be removed from the library. (Make this optional,
as one might want to have cached files from removable
media?)

4) Rescan all folders in Media Librar to see if there any
new files to be added. (Do this in the background with a
low priority of course.)

[Anders Sandvig]

Partially implemented. Needs options to toggle behavior.

[Anders Sandvig]

Basically implemented, but need some more testing (and possibly some tweaking).