Add submodule for diffpy.srfit.
Move to the common directory.
Added more diffpy git repositories as submodules.
Try to incorporate mercurial module.
Build order description.
Fix PyCifRW directory name.
Add cxxtest submodule.
Add INSTALL file for the bundle.
PyCifRW is in mercurial.

We shall use a zip file for sources.
Move submodules under the Linux tree.
Off with the gitmodules!
Ignore downloaded sources.
Download script for all dependencies.