tasks.rb: Apply HPXML modifications recursively

[shorowit]

In the update_hpxmls task, we only apply the HPXML modifications to the final HPXML path. This means that when one HPXML file references another as a parent, the parent's modifications are not applied and we have to explicitly specify that we want to apply the modifications again. This results in code like so:

OpenStudio-HPXML/tasks.rb

Lines 1451 to 1454 in 9332bad

	if ['base-enclosure-2stories-garage.xml',
	'base-enclosure-garage.xml',
	'base-zones-spaces.xml',
	'base-zones-spaces-multiple.xml'].include? hpxml_file

Even though base-zones-spaces.xml references base-enclosure-garage.xml as the parent, we have to include both of them in the code.

Instead, we can use the parent_hpxml_filenames array to recursively apply the modifications from all the parent HPXMLs too. This would simplify our code and be more expected/intuitive for a developer.