Enhancement: Extend cartridge collections to include custom cartridge properties and cartridge versioning

[nickdgriffin]

I think the cartridge collection functionality should be extended to include support for the following two capabilities:

• Custom cartridge properties (Added custom cartridge properties multi-line text field to load cartridge #52)
• Cartridge versioning (Enhancement: Load_Cartridge updated so it accepts a commitish object to use #57)

This enables a "cartridges as code" mentality where a collection can be used to version the loading of a cartridges along with their properties.