Fab automation (#2)

- Use KiKit for fab automation
- Add splitflap scripts for exporting pcb pdfs, and switch to splitflap script for 3d rendering (for consistency with fab automation)
- Added support in 3d rendering scripts for soldermask & silkscreen colors, option to skip virtual components
- Added silkscreen to base and screen pcbs for commit and date info

util/file_util.py

@@ -0,0 +1,14 @@
+#!/usr/bin/env python
+
+import errno
+import os
+
+def mkdir_p(path):
+    try:
+        os.makedirs(path)
+    except OSError as exc:  # Python >2.5
+        if exc.errno == errno.EEXIST and os.path.isdir(path):
+            pass
+        else:
+            raise
+