mpd: Make regexps work with re.VERBOSE
mpd: Remove redundant ^ from all patterns

re.match() only matches on the start of the line anyway.
mpd: Use same regexp flags everywhere
mpd: Reduce indentation of multiline regexps
mpd: Match just ' ', not any space char
mpd: Reformat query regexp
mpd: Move query_from_mpd_search_format into only module using it
mpd: Split out common query fields
mpd: Rename constants
mpd: Reformat list query pattern
mpd: Ensure quotes are matched
mpd: Sort search fields
mpd: Add note about use of re.VERBOSE
mpd: Remove redundant ^ anchor in example pattern
mpd: Register the two playlistid forms explicitly
mpd: Add TODOs for remaining quote matching
Merge pull request #584 from jodal/feature/mpd-regexp-improvements

MPD regexp improvements