TilesToROIs: don't make a subPixel ROI

All ROIs in this plugin were being constructed with doubles, which
causes ImageJ to treat them as having sub-pixel accuracy (and convert
them to ints anyway).

So instead we do the casts to ints ahead of time and avoid the sub-pixel
accuracy flag being set. This allows the ROIs to be modified in a way
one would typically expect of a ROI.
TilesToROIs: display all slices

TilesToROIs was processing all tiles, but many of them - when added as
ROIs - were discarded for being duplicates, as their slice index was
never set.

Tiles are now mapped to slice indices. Then the entire image stack is
created, with each resulting Roi indexed under the correct slice.

This allows visualization of all tiles in the dataset, and not just the
first tile discovered in each position.
TilesToROIs: add file name to ROI name

When creating Rois, the original Reader is used to look up the file
name, and that name is appended to the Roi name.

This allows each Roi displayed in the Roi Manager to indicate its origin
on disk.
TileUtils: normalize ROI unit calibration

When computing coordinates in TileUtils, the height and width of each
tile (on a per-series basis) are normalized to the first valid x,y
calibration values in the dataset.

If series 2 had a calibration of 0.5um and series 0 had a calibration of
0.1um, then each roi from series 2 would have its height and width
multiplied by (0.5 / 0.1).

Stage positions are also converted to uncalibrated units (position /
calibration).

This allows us report calibrated values in consumers of TileUtils.
TilesToROIs now applies the first calibrated values to the ImagePlus it
creates.. so it should be clearer what the actual size of the displayed
regions are.