Mpxj

* Fix percent complete NaN value for some Primavera schedules.

* Fix incorrectly set critical flag for primavera schedules.

* Updated to rtfparserkit 1.9.0 for improved RTF parsing
* Improve calendar exception parsing for Primavera XER and database readers.
* Ensure the task summary flag is set correctly for Primavera schedules.
* Rollup baseline, early and late start and finish dates to WBS for Primavera schedules.
* Rollup baseline duration, remaining duration and percent complete to WBS for Primavera schedules.
* Use the project's critical slack limit value when setting the critical flag on a task.
* Experimental support for reading Merlin Project schedules.

* Default to UTF-8 encoding when generating JSON files

* Correctly read text from MPP files when default charset is not UTF-8.
* Improve accuracy when reading MPP9 files.

* Add Primavera Parent Resource ID as a specific resource attribute (Based on a contribution by Dave McKay).
* PMXML writer generates currency record (Based on a contribution by Dave McKay).
* PMXML writer defaults Activity PercentCompleteType to Duration (Based on a contribution by Dave McKay).
* PMXML writer records currency and parent attributes for Resource (Based on a contribution by Dave McKay).
* PMXML writer resource assignments include RateSource and ActualOvertimeUnits attributes(Based on a contribution by Dave McKay).
* MSPDI reader: gracefully handle invalid calendar exceptions..
* PMXML writer: gracefully handle missing data.
* Planner writer: gracefully handle missing data.