Schema changes.

Rename fields:

UserAccount.user to UserAccount.person
CPUJob.user to CPUJob.person
UserCache.user to UserCache.person
ProjectCache.pid to ProjectCache.project

Rename models:

UserAccount to Account
UserCache to PersonCache

Rename other stuff related to the above.

Change-Id: Ieed5874001ba2db939eb2cb555eef80f6acef7cb