REPORT-582: runReport should flush session so other threads see updates to requests
REPORT-581: Evaluators throws exception if BaseCohort or ObsIdSet are empty
Merge pull request #55 from rowanseymour/requestflush

REPORT-582: runReport should flush session so other threads see updates ...
Protect against a case (I don't know why this is happening) where an exception in a task kills the task executor
More helpful static factory methods in Mapped
Added ageAtStart and ageAtEnd to the built-in patient data library
Update SqlUtils to improve validation that queries are select only, in order to fix bug reported in REPORT-585