[MZ] Style fixes.
[MZ] Namespace processing.
[MZ] Select longest artist by timespans.
[MZ] Refactored medium parsing into ParseMediumList.
[MZ] Artist browsing w/ releases instead of lookups.

Saves one additional request to MZ server per release.
[MZ] Removed old release-fetching code.

Obsoleted by 6c64684d61d3f6fd4c17dd22043824438f12e21a.