ImageJ-perpendicularThicknessTool: first release

The first release of my thickness measuring macro for ImageJ.

The intent of this macro was to measure the thickness of collagen forming around a polymer implant stained with picrosirius red.

Steps:
1) User uses line tool to mark the top edge of the polymer
2) User uses line tool to mark the top edge of the birefringent PSR stained collagen (polarized light).
3) Macro measures the perpendicular distance from line 1 to line 2 and records the distance.
4) Macro repeats measurement for every pixel along line 1 (user defined) until it reaches the end of the line.
5) Recorded measurements are shown immediately after the macro finishes.