Experimentally add build infrastructure and a few Tidy widgets

Experimentally add build infrastructure and a few Tidy widgets

For experimenting with using tidy, import TidyButton and TidyGrid
(+ dependencies) into our source tree and set up build machinery
to build them and build a typelib for them.

The sources are build right into libgnome-shell.so, so the Shell.gir
and Tidy.gir actually point to the same shared library.

src/Makefile-tidy.am: Build libtidy-1.0.la
src/Makefile.am: Include built tidy into gnome-shell.la and
  build Tidy-1.0.typelib

src/tidy/*: Add some source files from Tidy

svn path=/trunk/; revision=42