Icon picker: allow custom icons or custom URLs (#197)
Icon picker: allow custom icons or custom URLs (#197)

Add options to the icon picker to select custom registered icons
(according to http://docs.openhab.org/configuration/items.html#icons)
or a custom URL, without breaking the existing API.

Custom icons are "state-aware": for example, 'myicon' will display
myicon-on.svg resp. switch-off.svg when the item's state is 'ON' resp. 'OFF'.

Custom URLs includes all image formats supported by the browser:  SVG, PNG, JPEG, GIF etc.

Signed-off-by: Yannick Schaus <face5a63a8428ad87d6296bffc09b2e4f855592a@schaus.net>
ghys/habpanel,ghys/habpanel,openhab/org.openhab.ui.habpanel,openhab/org.openhab.ui.habpanel,openhab/org.openhab.ui.habpanel,openhab/org.openhab.ui.habpanel,ghys/habpanel,ghys/habpanel