(Renamed getSupportedCoreDirectiveNames to getSupportedBuiltInDirectiveNames)
(Some more date/time formatting tests)
(XML DOM Error message also mentions ?date.xs and ?time.xs)
1. New built-in: ?safe_substring. This is the same as ?substring, but it allows the begin index and/or the end index to be outside the bounds of the string.

2. Bug fixed: ?substring has thrown low level java.lang.IndexOutOfBoundsException-s instead of more descriptive TemplateModelException-s with FTL stack trace.