Fix parameter name in gitolite::repo

The gitolite::repo define uses 'authfile' and 'keydir' parameters, but its code
and defined declarations in gitolite::config use 'auth' and 'keys'.

Fix the discrepany by using 'authfile' and 'keydir' in all places.
Fix admin-update.sh fail when missing git user info

The script incation fails when gitolite user does not have git properties 'name'
and 'email' set properly. Add generation of .gitconfig rc file in
$gitolite::base to fix failure.