NOBUG: Installer to support gitlab master repos.

This creates a brand-new "gitmirror" clone with
all the remotes pointing to the new gitlab's master
repos. Both ssh and https remotes are supported.

Also, this commit gets rid of the old update.sh script
because we are not using the old mdlrelease manual
mehtod anymore.
NOBUG: Use new moodle-install repo for lang strings