* Sequence:
 - added hasOverlay(Class clazz) method
 - added getROI/2D/3Ds(boolean sorted) methods
* SearchBar: faster result display / refresh of search bar/
* Better internet connection monitor (lighter on network traffic).
* faster background repaint (cached), more responsive when moving
windows.
* fixed XLSUtil.loadWorkbook(..) which was clearing file.
* minor changes on VTK canvas shutdown.
* minor tweaks / improvements.
* refactoring.
Merge branch 'develop' of https://Stephane-D@github.com/Icy-imaging/Icy-Kernel.git into develop