Re-jig options handling to chassis and plugin specific sections

Currently all of the options, such as within the mysql-monitor-agent.ini file, are under a [mysql-proxy] specific option header. Many of the options listed here are in fact chassis specific, rather than for the proxy plugin.

This task is to split the options in the ini file to load by default the options specified under a [chassis] option header, and then load each of the options sections (by name) for each of the plugins to be loaded, such as [mysql-proxy], [mysql-monitor-agent], etc.