Give - Recurring Donations 2.9.0

* Tweak: Improved internationalization of the donor's choice checkbox language string.
* Fix: Improved SQL query structure for DB upgrade having issues on some database environments.
* Fix: PHP notice when clicking on a custom amount level.

* Fix: The update routine supposed to be release in 1.5.3 wasn't properly merged therefore we need this new release to ensure it goes out to everyone as expected.

* New: There is now a hidden field that can be used by other plugin authers to determine whether the given donation was recurring or not.
* Fix: Currency formatting was incorrect (too many decimal values would show) for the recurring helper text when choosing a recurring level.