Support deferred revenue accounting, etc.

This work has been funded by the IIDA. As part of the same project there are other enhancements (eg recording credit card type and last 4 digits) and bug fixes being done, but they are not included in this epic. Some of the work funded was merged into core but is now being broken out into extensions. Other parts will be developed as extensions.

1. Support enabling and disabling the following setting in CiviContribute Component Settings
2. Enable Deferred Revenue

1. Refactor support for financial account balances and closing financial periods into extension

(more to come)