This patch consolidates several aspects of the command handling in

This patch consolidates several aspects of the command handling in
rrdcached:

 * all commands, help, and context information is reduced to a single data
   structure.

 * all checks for command validity (context and permission) are handled in
   the main dispatch routine

This removes duplicate help/syntax text, and long if..elseif..else chains.
It facilitates the addition of new commands. -- kevin

git-svn-id: svn://svn.oetiker.ch/rrdtool/trunk/program@1788 a5681a0c-68f1-0310-ab6d-d61299d08faa