Evaluate size of overall CMCD data.

[PCaponetti]

Through conversations with video providers it became clear that CMCD may get greater market penetration if the size of the overall data was smaller. CMCD fills logs, and logs cost money to store, analyze, and propagate. One might point to the fact that all keys are optional in CMCD v1, and the vast majority are optional in v2, but there are many video providers using third party players that have only the ability to turn CMCD on or off as a whole, not by key.

This issue is meant to be evaluated late in the CMCD v2 definition to be able to look across all keys and decide whether something should be done to mitigate these size concerns. Thoughts include putting size constraints on keys, or maybe defining different verbosity levels that group keys together for different use cases.