Sheets.py now removes the scad files it generates.

Bodge for race condition on Win7.
Note PDF files have change due to new version of InkScape but should look the same.

stls.py

@@ -6,6 +6,7 @@ import shutil
 import sys
 import c14n_stl
 from set_machine import *
+from time import *
 
 from bom import source_dir
 
@@ -34,6 +35,7 @@ def stls(machine, parts = None):
     if os.path.isdir(target_dir):
         if not parts:
             shutil.rmtree(target_dir)   #if making the BOM clear the directory first
+            sleep(0.1)
             os.makedirs(target_dir)
     else:
         os.makedirs(target_dir)