Future-proof ij1-patcher for ImageJ 1.49m

This commit addresses the problem arising from ImageJ's version 1.49m
simply moving the JavaScriptEvaluator class into the ij.plugin package
with the following explanation:

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Merge pull request #32 from imagej/ij-1.49m

Future-proof ij1-patcher for ImageJ 1.49m