Ensure compatibility with d8
Don't submit unused os and cpu variables.
Merge pull request #9 from BenjBouv/v8-compat

Ensure compatibility with d8
Different submitters
Uses a config flag for the number of cores used for building
Allow selecting a subset of the engines to use
No native compilation as an option
Select MozillaInbound modes by option
Select benchmarks by option
Avoid polluting dostuff by moving modes selection in builders
Better presentation using OptionGroups
Better printer
Choose submitter by option
Merge branch 'submitter-printer'

Conflicts:
	driver/submitter.py