clean up of account_object definition and merge with rc_account_object

Other than renaming, rearrangement of members and some encapsulation, there are some other changes:

• accounts created during genesis now have proper creation date
• "steem" account is now created as genesis account, since its existence is required early due to it being used as default recovery agent up to HF11
• part of old tiny_asset related branch was added to finally push changes in that direction
• accidentally fixed problem of changed_recovery_account_operation vop always having old_recovery_account == new_recovery_account
• fixed long lived bug with power down (problem introduced in HF1 on accounts that started power down before that time)
• finally the main thing: data from rc_account_object moved to account_object

Needs schemas!44