* Icy let you select appropriate importer when multiple choice are
available.
* Loader: many changes to provide better support on
FileImporter and SequenceFileImporter classes.
* FileImporter.acceptFile(..) method now use path parameter.
* Layers panel:
 - opacity setting has moved at bottom.
 - support custom setting panel per layer (Overlay.getOptionsPanel())
* SequenceUtil:
 - C/Z/T merge operation now preserve metadata.
 - added getSubSequence(Sequence, ROI, double) method.
* User email information stored in preferences.
* some refactoring:
 - ImageLoaderDialog --> LoaderDialog
 - ImageSaverDialog --> SaverDialog
 - LoadDialog --> OpenDialog
* others minors improvements, bug fixes and cleanup.