Use the build tools written in C

The build tools in C are far from finished, but it's better to use them
as soon as possible, so it will be better tested.
Rename Latexila -> LatexilaApp (in Vala)

Because there is a conflict with the Latexila namespace used by the
liblatexila.
Use Latexila.BuildView
Port BuildToolDialog to the build tools written in C