mlaunch: ignore processes which don't have --port

Fixes #297.
Merge pull request #298 from devkev/foreignmongods

mlaunch: ignore processes which don't have --port
Merge branch 'feature-269-2.7-plus-logging' of github.com:jimoleary/mtools into jimoleary-feature-269-2.7-plus-logging
improved help text for mlogfilter options.
only allow valid choices for mlogfilter options
Merge pull request #1 from rueckstiess/jimoleary-feature-269-2.7-plus-logging

improved mlogfilter help and only allow valid option choices