ADDED:
```REIXSXESImageInterpolationABEditor::onShift1LineEdited()``` and
connected to line edit to enable manual shift entry for curve 1
FIXED:
in ```REIXSXESImageInterpolationAB::computeCachedValues()```:

-bug in shifting algorithm: by truncating each shift map value before
multiplying by the interpolation level, sub-pixel shifting wasn't
happening and interpolating the image was a complete waste.

-reversed the shifting algorithm so that each pixel in the shifted image
grabs one pixel value from the interpolated image - as determined by the
shift value at the point - instead of placing each pixel from the
interpolated image into a pixel in the shifted image, which results in
over/under filled pixels. I don't understand how Robert's code ever
worked doing it the latter way.
CLEANUP:
Remove commented out code
MODIFIED:
Tweak plot colors for maximum visability against bone color map
MODIFIED:

-Make the new REIXSXESImageInterpolationAB the default AB for XES scans.