The installer now uses the HTTPS protocol for submodules

I just merged a change made by Greg to the foreman-installer repository to use the HTTPS protocol instead of git when cloning submodules. A number of people had issues using the installer because corporate firewalls often block certain protocols; git among them. If you have an existing clone of the installer and want to update it to use HTTPS, run git submodule sync; all fresh clones will use HTTPS going forward.

Let me know if you have any issues.