Release 3.14.0 - Pi version!

It's easier to follow GNOME versions. For the packagers, for the users,
for the contributors, and for the maintainers. When creating a
latexila-x-y branch, a mail must be manually sent to the GNOME
translation and documenation teams, which is not convenient. On the
other hand, when creating a gnome-x-y branch, mails are sent
automatically.

The 2.0 version was chosen because there was a major code change (a
complete rewrite). But now only incremental changes are made every six
months.
Fix regex in latex post-processor

In pdftex.web (in the source code of TeXLive), we can see:
print(") has occurred while \output is active")

But in a regex the backslash must be escaped. (And in a C string the
backslash must be escaped too, so there are 4 '\').
Fix icon for Cleanup Build Files
desktop entry: add WordProcessor category
Fix Vala warning

warning: accessibility of struct fields can only be `public`
Override some CSS properties for Adwaita
Create liblatexila with empty GObject class

The liblatexila is not a real library like GTK+, it is just an internal
library. The code will be written in C in this directory. The Vala code
in the parent directory can use the liblatexila, but I'll try to not do
the reverse (use the Vala code in liblatexila) so the liblatexila is
self-contained and could be reused easily by other projects (a gedit
plugin for example).

Why the C language? Well, I now prefer the C language. The Vala syntax
is nice, but it adds another layer. Another layer of potential bugs.
Another layer of maintenance. Another layer for the API documentation.
The GNOME documentation with GTK-Doc is primarily written for the C
language. And the verbosity of the C language has advantages
("greppable" code, code more self-documented).
build: use GNOME_COMPILE_WARNINGS

For the C code in the liblatexila it's important.
Update the hacking file
LatexilaPostProcessor base class
LatexilaPostProcessorAllOutput
Add 'priv' in the object structs

I don't like using all the time get_instance_private().
LatexilaBuildTools classes

And add a latexila-types.h for convenience.
Add GObject introspection support

It will be used to generate the .vapi for the liblatexila.
Generate latexila.vapi with GObject Introspection
latexila.h to ease introspection support
build tools: add missing GI annotations
Generate internal GTK-Doc documentation
Doc fixes
BuildTool and BuildJob classes

And add enum types.