- added battery holder for 2 x 3 aaa battery holders
- Made the top of the main device flat, so it's easier to 3D printer using plastic extrusion
- tightened tolerance around main circuit board
- increased the thickness to 2mm in back (near plug) and 3mm in front (near detector)
--- this is first test run by carrythewhat.

Signed-off-by:  <Greg>