Refactor and remove unused stuff
Refactor and remove unused stuff

- Replace TestContext.daoFactory with a DaoSpiFactory and a QuotaCharger (since
  DaoFactory no longer exists, was removed in debiki-core)
- Remove TestContext.createRestorePoint(), revertToRestorePoint()
- Let TestContextBuilder be a trait, not a Function2[...] type

debiki/debiki-server-old,debiki/debiki-server-old,debiki/debiki-server-old,debiki/debiki-server-old