local: Add albumartist support to search/find_exact
mpd: Make 'list' support 'albumartist' key
local: Include albumartist in 'any' searches
Merge branch 'develop' into feature/search-by-albumartist

Conflicts:
	tests/backends/local/library_test.py
local: Remove redundant test asserts
Merge pull request #532 from jodal/feature/search-by-albumartist

Search filtering by albumartist