Fix rebase conflicts. Remove Profile presentation aspects and binding to Git.

This removes Profile.getIconURL(), getSummaryMarkdown(), get/setTags()
Profiles is an immutable data structure that is built through ProfileBuilder
We need to decide how IconURL & SummaryMarkdown can be part of a consistent/atomic update.
So far Profile is independent of Git. Again, we need to decide how the notion of Profile tags can be part of the copy-modify-update model.