Modifications for legacy systematic setup.
Allows different types of systematic:
	- Per photon category scales and smears (can be correlated across years or not)
	- Global scales (can be correlated across years or not)

Also added a small feature to allow VH dijet category to appear above ttH categories in signal composition plot.
Merge pull request #364 from matthewkenzie/systematics_mods_for_legacy_result

Modifications for legacy systematic setup.