Modify TimeInterval restrictions

[dylan-sa]

In #925, we settled on adding actualStartDateTime and actualEndDateTime restrictions to TimeInterval. @rjyounes has pointed out that the definitions of these predicates are phrased in the past tense, making them not a good fit for future time intervals. For this reason, we have kept the restrictions out of the 13.0 release.

Assuming dateTime restrictions would be good to have on TimeInterval, one option is to modify the definitions for actualStartDateTime and actualEndDateTime to include known datetimes in the future, even if we haven't reached them yet.

[dylan-sa]

Decision: use startDateTime and endDateTime predicates in the restriction instead. Update annotations for these predicates to clarify usage.

[rjyounes]

DECISION:

• Change restrictions from actual dates to endDateTime and startDateTime.
• Modify definitions of those predicates to use present rather than past tense (e.g., "starts" rather than "started").
• Modify/add scope notes to say that generally these will not be asserted, and possibly mention the example of TimeInterval as a case where they would be.