[Builder] Switching to Meson

[Christian Hergert <christian hergert me>]

We've long been talking about Builder moving to Meson for it's build
system. I intend to flip the switch to "Meson Only" tomorrow, June 5th.

I decided to include as part of this switch the removal of some contrib
libraries to favor externally installed versions. This includes
libdazzle, jsonrpc-glib, and template-glib. These projects are already
in jhbuild and therefore will be automatically installed should you run
"jhbuild build gnome-builder".

If you are the type of jhbuild user that generally does "buildone", note
you might need to install these libraries first.

What this means to you:

 - If you build Builder with JHBuild: Nothing.

 - If you use Builder to build Builder, you might just have to re-open
the Builder project so it can locate the new build system.

 - If you are building on the command line manually, you can try
something like this:

  meson \
   --prefix=/opt/gnome \
   --libdir=/opt/gnome/lib \
   -Denable_tracing=true \
   -Denable_profiling=true \
   . \
   _build
 cd _build
 ninja

It's a little annoying at first changing your muscle memory, but I
assure you the build times are absolutely worth it. It's incredibly
impressive, even to an old curmudgeon like me.

-- Christian