Factor out the common parts of of the hoq* scripts

Also add hoqdep
Move hoq-config script to top-level

This way, we can copy it more easily.
Bundle coq

This will hopefully pave the way to make it easier to build coq for new
users.
Auto-init the bundled coq on autogen.sh
Call HoTT/coq configure on ./configure
WIP bundle coq
Fix symlinks