Bugfixes & Icons

- image import more robust
- import & organise now recognise if mesh items are selected. Selection
sets are created for selection. If no mesh is selected and a $ENTITY is
given all textures are imported if theses have correspondent mesh items
in the scene.
- the filename variable extraction is now more robust -> re.escape and
replace is used to create a clean delimiter for re.split
- former delimiter method get_UDIM() was removed as well as the user
value query for the delimiter
- not imported images are logged in the log window
-Icons for all functions