This change adds an account freeze service with methods for checking
if a user is frozen, freezing a user, and unfreezing a user.
Furthermore, methods for altering the usage limits of a user or project
have been implemented for use by the account freeze service.
Change-Id: I77fecfac5c152f134bec90165acfe4f1dea957e7
This change implements DB methods for interacting with the
account_freeze_event table and introduces structures related to
account freeze events.
Change-Id: Ib125b31dfb754b2428212c39b780e14cfc7f97bf