fix problem with proxy that arises from compile time code values on the old singleton and the bugfix for reading other contracts

using primary_upper_bound instead of next_primary in identity contract (next_primary doesn't work as I expect)

bugfixes in singleton, bugfixes in identity contract, more tests for identity contracts (one fails because of bug in next_primary)

back to singleton for accounts, bugfixes in db api, test for trusted owner (fails because primary_lower_bound doesn't work as I expected)