* fixed ROI panel NPE.
* fixed minor bug with Viewer.setCanvas() method.
* faulty plugins (corrupted jar file) are now automatically reinstalled.
* fixed ROIUtil.getMassCenter() method.
* fixed pixel size calculation on image resize operation.
* fixed bug on ROI opacity change.
* fixed LOD for ROI2DPoint and ROI2DLine.
* minors fixes / improvements.