Handle instance type "generations" (Amazon)

[László Puskás]

Find a way to weight older instance families, like m1: these instance types have the same amount of memory/cpu cores like newer instance families but fall behind in performance because of older underlying hardware. They tend to be cheaper because of this, so the recommendation often finds these types. In phase 1, find a very straightforward way to weight them, like computing with +50% cost for these types (or completely exclude very old types from the recommendation). (P0) In phase 2, we can find a way to benchmark instance types and weight the recommendations accordingly.