[megascan-assembler] load recipes from data files instead of hardcoding them

[Mike]

The general format of each 'recipe' is something like: "Take a bunch of files and bundle each one into a varying number of channels."

Examples we have:

• _n.tga is produced from *Normal.jpg (mandatory) (one to many)
• _a_d.tga is produced from *Albedo.jpg mapped over RGB and *Displacement.jpg mapped over A (one to many + one to one)
• _m_r_c_ao.tga is produced from *Metallic.jpg (optional), *Roughness.jpg, *Cavity.jpg, *AO.jpg mapped to R, G, B, A respectively (one to one)

We can generically implement one-to-one and one-to-many recipes and build a parser that reads an input datafile for any arbitrary demands on this system. That way, we can support new bundle formats as they are required (I think there is at least one new one that Trent needs that this one does not currently support, though it is quite rare).

[Trent Polack]

Closing: 4bd8302