make site-local scripts easier to write

- new Gitolite::Easy module hides all the other stuff
  - (put GL_ADMIN_BASE and GL_REPO_BASE into %ENV)
  - new 'gitolite creator' shell command
  - 'writes' command modified to use Gitolite::Easy.  It is also the
    only dual mode command -- it can be invoked remotely as well as
    locally.  I deem that the required trick to make other remote-only
    commands work locally is too much trouble for what is probably a
    rarely used command.

t/glt

@@ -13,6 +13,7 @@ my %extcmds = (
     help        => 1,
     info        => 1,
     perms       => 1,
+    writes      => 1,
 );
 
 $ENV{G3T_USER} = $user;