* Add a detail_size field to the Sculpt struct, two new sculpt flags,
and a Mesh flag for dynamic-topology mode; that's it for file-level
changes needed by dynamic topology
* Add RNA for the new DNA field and flags
* Add a new icon for dynamic-topology created by Julio Iglesias. TODO:
update the icon for the new SVG icon format
* Add a SculptSession function for converting from BMesh to Mesh,
handles reordering mesh elements and setting face shading