Add batch file command line options and parse batch files on startup.

Still doesn't do anything...
Fix filename duplication detection for scale files.
Add example batch file.
Move formatter and aggregator loading code into their respective modules.
Kill child processes with SIGTERM on keyboard interrupt.
Honour SIGINT while running the GUI.
Try harder to exit nicely when killed.
Code refactoring in preparation for the batch mode implementation.

Control flow decisions moved out of the settings module and the main
netperf-wrapper binary to instead live in the batch module.
Batch mode runs tests, although the functionality is still incomplete.
Support setting --remote-metadata from the rc file and make it imply --extended-metadata.
Batch mode kinda-sorta feature complete.
Merge branch 'master' of github.com:tohojo/netperf-wrapper