Add play and pause commands

Add commands that always play and always pause, in addition to the
current toggle pause command.

Closes #342.
Merge remote-tracking branch 'promy/master'

Conflicts:
	src/settings.h
	src/ui_act.h
	src/ui_dispatch.h
piano: Add error message for code 1039

See #352.
Stop playback if audio file is not accessible

See #352.
Transform actual station when loving/banning songs

Loving/banning a song from a shared station while playing quickmix
resulted in “call not allowed”, because we tried to transform the
quickmix instead of the song’s real station. Fixes #354.
Fix station name when deleting a station
makefile: use ":=" when using $(shell pkg-config...) to avoid duplicate evaluations

This speeds up the make process.
Merge remote-tracking branch 'promy/master'
Add missing events to genre station selection

Two new events: stationfetchgenre, stationaddgenre
Ignore HTTP status 400

Workaround for #355, fixes commit
2c516503d2cb81dd156afc24677ac4bf3caefceb.
Merge remote-tracking branch 'promy/master'
Merge branch 'master' into dl

Conflicts:
	src/player.c
	src/settings.h