Include cell counts of microwells in secretion analysis

Allow inclusion of a point roi indicating cell locations to be used to
determine the number of cells in a microwell to be used along with
analysis of secretion per bead signal.
Add ability to import ND2 Datasets directly

Needed to import scifio and scifio-bf-compat
Tested it in PointTester
Created a ui dialog on the Script panel of JEX
Created and associated JEXPlugin that takes file paths in a Value
Object to feed in multiple file paths to import many ND2 files at once.

Updated capitalization of Static string variable names in
MarkerConstants to be more consistent.