pushing: eliminate perl from the push path

pushing: eliminate perl from the push path

Since e2942ff1 perl has no longer been loaded just to export the
Config.pm variables.  However, that was not enough to eliminate
perl from the non-ssh push path.

Switch from using Project.pm and User.pm to do can_user_push
checks and UUID checks when using smart HTTP push to the new
can_user_push_http and get_user_uuid utilities to avoid needing
to load the perl interpreter on every non-ssh push.