Create & publish a snap version

[cimm]

A snap would be easier to install for Linux people since they don't have to install all the dependencies and compile the whole thing.

The end goal should is to simplify installation to:

snap install codav

[cimm]

I have it working locally. The GResources change (b23fbc5) really helped simplifying the build instructions.

Not sure if I want to give the snap access to the full filesystem or confine it.

Confinement is probably a good idea, CODAv simply opens files, no need to give it full access, but... the GTK open file dialog might not show the correct errors when trying to navigate around. Ideas?

Another issue is the .desktop file, not sure how to move that to the right place yet.

[cimm]

The YAML file includes Unity, not sure if we still need this. Wouldn't it be better to depend on GNOME now that Ubuntu 17.10 (and the upcoming LTS) no longer use Unity?

[cimm]

We now have a working snap for X11 sessions:

snap install codav --edge

It does not work on Wayland yet. There is a workaround available but it means adding a PPA before building the snap which will not work on build.snapcraft.io. The Wayland work around also does not seem to detect HDMI screens.

The .desktop file does work now, it was simply pointing to the wrong path earlier.

To answer my earlier question: the unity7 plug is still needed for older desktops, it's possible to support both X11 and Wayland in the same snap.