Packaging Advanced Gtk+ Sequencer v0.7.56

[Joël Krähemann]

Hi all

Last 2 months I have investigated much in stabilize GSequencer's 0.7.x
branch. What about packaging for debian? It would be great having the
new features in debian.

For now I proceed in 0.8.x branch that stable code doesn't get in
touch with experimental one.

New is DSSI and Lv2 support as well the automation editor. Further
many improvements are done like configuration in place.

Bests,
Joël