Add support for configuring named groups of custom call features in

features.conf.  This allows you to create a feature one time, and then map it
into groups for various different key mappings for the same feature, as well
as easy access control to groups of features.
(patch from bbryant)


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@66774 65c4cc65-6c06-0410-ace0-fbb531ad65f3