Add more conditions to advanced search architecture

[dstillman]

Add support for tags, creators, etc. as advanced search conditions

[dstillman]

(In [442]) Addresses #171, Add more conditions to advanced search architecture

Added conditions 'tagID', 'tag' (text), 'creator' (concats first and last before comparing), and 'note'

[dstillman]

(In [452]) Addresses #171, Add more conditions to advanced search architecture

• Implemented 'collectionID' and 'savedSearchID' conditions (a.k.a. search within a search) and removed special 'context' condition. Per my conversation with Dan, the 'recursive' flag is now a global flag that applies to all specified collectionIDs, which is less than ideal but probably better than the alternatives (e.g. having condition-specific recursive checkboxes). It does mean, however, that a "Search subfolders" checkbox is irrelevant if there are no collectionID conditions and should probably be greyed out until applicable.

Another side effect is that it's no longer possible to do an ANY search and return results only within a specific folder (though it can now be done by putting the ANY conditions in a subsearch). Since ANY searches are always annoying in this regard, what I might do is add a way to mark particular conditions as required even in ANY mode, which would allow for quite a lot of flexibility...

Note also that while 'collectionID' and 'savedSearchID' are standard conditions, they should probably be combined into a single condition on the interface side (like playlists and smart playlists under just 'Playlist' in iTunes).

• Now skips invalid/obsolete saved conditions in load()

[dstillman]

Added #175 for required conditions enhancement.