Updated Fixed Base

Updated the fixed base in SketchUp.  It's much stronger now and uses
dovetails and hammer forced connections.  Deleted the old DXF as it is
now out of date.
Creating new permanent workbench

Creating a new permanent workbench file to print.  Got the desired
dimensions in Grasshopper/Rhino.  Saved as SKP file.  Created new
SketchUp file and combined top and base in SketchUp.