This also updates all other plugins that rely on process listing
and theoretically allows them to choose their preferred method of
process listing. At the moment, the default (first in the method list)
is chosen. An optional pslist_method StringRequirement can be added to
each plugin, but using the list in the requirements could break if the
pslist plugin is too old (ie, using the list would happen before the
PluginRequirement gets checked).
If this is a feature we want, it should be easy to add to all but
netstat, which does not parameterize the list of processes.