Implementation for setting max volume (#336)

* Added support for creating a max volume

* Fixed db function calls

* Fixed issue with max volume always adjusting volume

configuration.default.ini

@@ -49,6 +49,7 @@ language = en_US
 logfile =
 max_track_duration = 60
 max_track_playlist = 20
+max_volume = 1.0
 music_database_path = music.db
 music_folder = music_folder/
 pip3_path = venv/bin/pip
@@ -117,6 +118,7 @@ kill = kill
 last = last
 list_file = listfile
 list_webinterface_user = webuserlist
+max_volume = maxvolume
 mode = mode
 pause = pause
 play = p, play