Bug: 12869  Fix importing RRULE UNTIL values when they contain date parts.

We were already treating UNTIL as inclusive as well as comparing them by datetime
(as opposed to date). The problem was we weren't importing the time portion
of the UNTIL value if it was present.
Fix existing tests for UNTIL values.

These are inclusive, and compared via datetime values, so we MUST
persist the full datetime when parsing the RRULE.
Add new test for Bug: 12869
BFN