Adds Image service v1 and v2 specification info in general

Goal is to maintain API specs in the specs repo for each project
and to eliminate the image-api repo.

Splits up original v2 API document into multiple files.

Change-Id: I7b6fbb1ee4a9a2e04395a7aa942d9ebdb011cc85
Merge "Adds Image service v1 and v2 specification info in general"