configuration samples: Pull all parking related stuff out of features.conf

This patch also adds documentation for parking from features.conf to
res_parking.conf
........

Merged revisions 400205 from http://svn.asterisk.org/svn/asterisk/branches/12


git-svn-id: http://svn.asterisk.org/svn/asterisk/trunk@400206 f38db490-d61c-443f-a65b-d21fe96a405b