[collectd] improve Processes plugin

[Lukas Bednar]

Hi all,

we use collectd to monitor specific processes on our
machines. But there is problem that these specific
processes execute another processes (children) which
generate considerable load. These child-processes isn't
counted to statistic data of specific process. So we would
like improve this plugin with ProcessTree and
ProcessMatchTree option.

I would like know whether there is no similar
functionality in order avoid to duplicity.

Great regards,

Lukas.