personal branches: de-emphasise old-style, document new-style

There are some disadvantages to the old-style personal branch scheme.
It only allows one specific pattern (of refname) to be used, forces that
pattern to be applicable to *all* repos in the entire config, and
requires editing the rc file (on the server) to be edited to achieve
this.

In other words, it's a very blunt instrument...

The new style depends on using lines like this within a specific repo
config:

        RW+ personal/USER/      =   @userlist

The important thing is that the "branch" name should contain `/USER/`
(including the slashes).  Access is still determined by the right hand
side of course.

This gives you the following advantages:

  - allow it only for repos that need it
  - allow different patterns to be used for different repos
  - allow *multiple* patterns; just add more than one such line
  - allow the pattern to have suffixes (eg: foo/USER/bar)

conf/example.gitolite.rc

@@ -65,26 +65,6 @@ $GL_CONF_COMPILED="$GL_ADMINDIR/conf/gitolite.conf-compiled.pm";
 
 # --------------------------------------
 
-# personal branch prefix; leave it as is (empty) if you don't want to use the
-# feature (see the "developer-specific branches" section in the "faq, tips,
-# etc" document)
-
-$PERSONAL="";
-
-# uncomment one of these if you do want it.  If you change it, remember it
-# MUST start with "refs/"
-
-# I recommend this:
-# $PERSONAL="refs/personal";
-
-# if you want something more visible/noisy, use this:
-# $PERSONAL="refs/heads/personal";
-
-# NOTE: whatever value you choose, for security reasons it is better to make
-# it fully qualified -- that is, starting with "refs/"
-
-# --------------------------------------
-
 # if git on your server is on a standard path (that is
 #       ssh git@server git --version
 # works), leave this setting as is.  Otherwise, choose one of the