Add Generation Map to Instance Page

Show where existing generation is relative to all generations.

Example for c5:

+2 gen: c7g
+1 gen: c6g, c6a, c6i
current: c5
-1 gen: c4
-2 gen: c3
-3 gen: c2 
-4 gen: c1

I know that an API for this is also highly desirable and not currently made by AWS but was heavily requested

