Make the status bar smaller

Maybe something changed again in GTK+. With GTK+ 3.13.7 the status bar
was a little too big in my opinion. Now it should be fixed (again).
Add completion menu item (ctrl+space)

The Ctrl+space shortcut was documented nowhere in the interface, only in
the documentation. Now with the menu item, the Ctrl+space shortcut is
more discoverable.

Several years ago there was a bug with the "fr oss" keyboard layout: a
space (without the Ctrl modifier pressed) triggered Ctrl+space, see
https://bugzilla.gnome.org/show_bug.cgi?id=611089
It seems to be fixed now.
Updated Czech translation
Other build tools icons

Licensed under GNU LGPL v3 or Creative Commons BY-SA 3.0

Authors: GNOME Project (http://www.gnome.org)
Alexander Wilms <f.alexander.wilms@gmail.com>
Miroslav Mazel <mazelm@gmail.com>
Updated Dutch translation Master
Completion: add some comments
French translation update
Updated Indonesian translation
Updated German translation
Updated Polish translation
Updated Ukrainian translation
Updated Hungarian translation
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.