This commit modifies substitute.pl to parse 'parameters' specified in the options file.

A Parameter block looks like this:

	*ext-parameters:start

		*param:BaseUpgradeCost = 14216.602
		*param:BaseUtilitiesCost = 1447
		*param:PVTarrifDollarsPerkWh = 0.08

	ext-parameters:end

Parameters allow users to overide the default PV tarrifs and upgrade costs, as well as specifying the basic utility
costs. Substitute.pl now reports the simple payback period to the output file as well.
Merge branch 'master' of https://github.com/NRCan-IETS-CE-O-HBC/HousingModels
Bug fixes.
Adding parameters.
Merge branch 'master' of https://github.com/NRCan-IETS-CE-O-HBC/HousingModels