Fixed CountJointOccurrences not passing unit tests (fixes #305)
CountJointOccurrences could return true where parts of the input data was masked. Now, it will return false for any masked data. Since this function counts the number of occurrences, any masked data will now be counted as "not occurred".
Strict masking has been implemented such that any masked input data in a gridcell will result in that gridcell being masked in the output.
Edited by Carolina Nilsson