Change certain core configs into registered options.
Review Request #1373 - Created Nov. 21, 2014 and submitted
|jsirois, patricklaw, zundel|
These are options like pants_workdir, whose values can be interpolated
into pants.ini to create values for other options. So we treat them
specially: We refer to them as "bootstrap options" and we determine their
values in an early pass before getting the values for all the other options.
This allows, e.g., overriding --pants-workdir on the cmd line, like any other
option, but still having %(pants_workdir)s interpolations in config files
work as expected.
Added a test and removed some copy-pased code.
Revision 2 (+340 -170)