2019.05.03

Add support for hotkeys. #20

Hotkeys can be assigned to action in configuration file ex:
hk_<action_name> = g + shift + alt + ctrl

Available actions:

act_help                    -   prints help
act_songlove                -   love song
act_songban                 -   ban song
act_stationaddmusic         -   add music to station
act_stationcreate           -   create new station
act_stationdelete           -   delete station
act_songexplain             -   explain why this song is played
act_stationaddbygenre       -   add genre station
act_history                 -   song history
act_songinfo                -   print information about song/station
act_addshared               -   add shared station
act_songnext                -   next song
act_songpausetoggle         -   pause/resume playback
act_quit                    -   quit
act_stationrename           -   rename station
act_stationchange           -   change station
act_songtired               -   tired (ban song for 1 month
act_upcoming                -   upcoming songs
act_stationselectquickmix   -   select quickmix stations
act_bookmark                -   bookmark song/artist
act_voldown                 -   decrease volume
act_volup                   -   increase volume
act_managestation           -   delete seeds/feedback
act_stationcreatefromsong   -   create new station from song or artist
act_songplay                -   resume playback
act_songpause               -   pause playback
act_volreset                -   reset volume
act_settings                -   change settings