Mock RBAC, entitlements for mock SSO

[john-dupuy]

• Added entitlements and permissions fields to user model in TinyDB, these are string fields that are just comma-separated lists:

  entitlements: "advisor,ansible,settings"

• Added entitlements and permissions fields to UI table and form
• Added code to examine X-Rh-Identity header in requests and lookup user in TinyDB and return entitlements/permissions present on the user. If entitlements/permissions are None, return defaults

Meant to address #2, note that this PR does not handle resourceDefinitions or the is_trial part of the entitlements endpoint.

[skarekrow]

From my end, what I saw is good now. I'll leave final say to Squizz.