(MCO-272) Add ability splay registration plugins

This commit adds the registration_splay global configuration option.
When set starting the registration thread will be delayed by a random
amount of seconds between 0 and the registation interval.
Merge pull request #222 from ploubser/mco-272

(MCO-272) Add ability splay registration plugins
MCO-193 add 'discovery_timeout' to the configuration file

Here we add a discovery_timeout option to the configuration file, which is
allows you to set a default for the --discovery-timeout cli option.