Fix argument to autogen.sh

Now it consistently takes --disable-bundled-coq.

Reported By: Gaetan Gilbert
Make coqide by default

Previously, to get hoqide, you were required to change to the coq-HoTT
directory and `make coqide` manually.  Now, there are `coqide` and
`install-coqide` targets of the toplevel makefile.  Additionally, if you
don't pass --without-coqide to configure, then the `coqide` target is
made by default.  You will still have to `make install-coqide` manually,
though.

Reported By: Gaetan Gilbert
--disable-bundled-coq -> --without-bundled-coq

For consistency with, e.g., --without-coqide.  The version of Coq to use
is more like an (optional) external dependency, and less like a feature.
Merge branch 'bundle-coq' of github.com:JasonGross/HoTT