- Add DnD support to icon view - drag works, but drop doesn't for some reason!

- Rename FileView::setType() and getType() to type(), for consistency with 
fltk
- Fix hiding of views in type()
- Remove some old commented code (shouldn't be needed ever again)
- Make the selecion box around icons rounded
- Show "directory not found" error when needed (previously, efiler would 
silently jump to home)
- Fix DirTree not respecting default settings
- Attempt to fix callback for dirtree - impossible - documented in BUGS so 
someone could fix it someday
- Selecting with Space key and increasing selection by holding down shift

efiler/BUGS

@@ -0,0 +1,9 @@
+Known bugs:
+
+- If you execute cut, then drag&drop files from another window, cut operation 
+will be assumed.
+- Callback for tree view widget is erratic - it usually doesn't work on Enter 
+key and sometimes it is sufficient to press arrow up or down to enter a 
+directory.
+- In icon view, holding shift while clicking has the same effect as ctrl (i.e.
+adds just the focused widget to selection, not the ones in between)