Use GROUPLIST_PGM rc hidden feature of gitolite.

M  .gitignore:
  Ignore '/gitolite/ldap/', used for ldap group caching
A  gitolite/gitolite-ldap.tpl:
  Template for fetching ldap group
A  gitolite/gitolite-shell.tpl:
  Template moved from sbin
M  gitolite/install_or_update_gitolite.sh:
  cp_tpl templates including ldap pgm, mkdir ldap
D  sbin/gitolite-shell.tpl:
  Moved to /gitolite