Hmmm. Nobody (but me) is interested in seeing

Hmmm. Nobody (but me) is interested in seeing
the trie info when they do 'dialplan show ...'
(even with debug set to non-zero); so I set up a
   'dialplan debug [context]' cli command instead,
to explicitly show just the trie info.  I even
added an extension_exists() call to make sure the
trie info is built. I moved the explanatory header
to above the extension loop to ensure it only prints
once. And it will do this now, whether debug is set
or not.

I removed the trie printing from the 'dialplan show'
command entirely.

git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@148519 65c4cc65-6c06-0410-ace0-fbb531ad65f3