Consolidate GTK app Code.as / GitHub repos

[BrainBlasted]

This PR takes care of the work needed to bring the Code.as and GitHub codebases into one space. The main changes:

• The dependencies are no longer bundled, using only submodules
• The app ID is set dynamically with meson

[thebaer]

Excellent, thanks @BrainBlasted!

Changes all look good to me -- it just looks like there's a build issue with elementary's stuff. Could you take a look at that? Or should we fix that separately?

[BrainBlasted]

I "fixed" it, but that involved reverting the changes around gb. We'll have to see if I can get gb to work for the flatpak build, then.

[thebaer]

Alright, sounds good. We should be set for the scope of this task, at least.

Do we need to update the build instructions in the README, too? With a clean repo, when I run meson build now I get this output / error:

The Meson build system
Version: 0.51.1
Source dir: /home/mattbaer/projects/gtk/writeas-gtk
Build dir: /home/mattbaer/projects/gtk/writeas-gtk/build
Build type: native build
Project name: writeas-gtk
Project version: 1.0.2
C compiler for the build machine: cc (gcc 7.3.0 "cc (Ubuntu 7.3.0-27ubuntu1~18.04) 7.3.0")
Vala compiler for the build machine: valac (valac 0.40.11)
C compiler for the host machine: cc (gcc 7.3.0 "cc (Ubuntu 7.3.0-27ubuntu1~18.04) 7.3.0")
Vala compiler for the host machine: valac (valac 0.40.11)
Build machine cpu family: x86_64
Build machine cpu: x86_64
Configuring config.h using configuration
Configuring writeas-gtk.desktop using configuration
Configuring writeas-gtk.appdata.xml using configuration
Found pkg-config: /usr/bin/pkg-config (0.29.1)
Run-time dependency gtk+-3.0 found: YES 3.22.30
Run-time dependency gtksourceview-3.0 found: YES 3.24.7

meson.build:24:0: ERROR: Non-existent build file 'fonts/lora/meson.build'

[BrainBlasted]

You need to do a recursive clone or initialize the submodules after cloning.

[BrainBlasted]

Note: that aspect isn't different from the current master branch. So the directions could use an update, but that's unrelated to this PR.

[thebaer]

Thanks, I'd forgotten about that. Everything builds just fine 👍

There's just one last difference between the normal Code.as build and the GitHub / elementary version: the Code.as build didn't include the changes in #14.

If it's possible, and if there's no compelling reason not to do this, I'd like to keep the small icons in the writeas-gtk build and the large icons in the com.github.writeas.writeas-gtk build. What do you think?

[BrainBlasted]

Done. I think this should be good to go once this pipeline finishes.

[thebaer]

Awesome, looks great! Merging now.