volume: Use a new volume script

This new script can use different method to set the volume. For now only
the pulse audio method is available.
umonse-schedule: Add copyright information

This patch adds copyright information to the umons-schedule script.
purple-song-remote: Use nil instead of title

When using the end remote call we should use the special value "*"
instead of the title to remove the title.
volume: Add the aosd display

This patch adds a configurable aosd display to the volume script.
volume: Use a fond for the OSD

This patch use a new font variable for the OSD.
volume: Add support for default increment

This patch adds the support for a default increment value to the volume
script.