first test of raspberry base

We cleaned the 4dof arm and put it in a dedicated repo. This repo now only contains poppy-ergo-jr stuff.

STL are below and BOM is under hardware/parts/BOM.md

Hi there!

New stuff:

• pen holder
• poppy-4dof-arm-mini
• generate only the elementary parts so printing is easier and cheaper
• alpha raspberry base (requires a fix of stl, see below)

Info for printing:

• Check the visuals to see how all this looks like.
• Use the BOM.pdf to know the quantity of each to print for each robot (check if no errors of course).
• The corresponding stls are in the parts folder. I generated them with zero tolerance. If it prints as the first batch it should work fine, but do not print 10 robots please! we are still testing things. You can visualize them using http://www.viewstl.com/ if needed.
• A raspberry base can be found in repo/hardware/specific_frames/raspberry_base_frame.scad. There is a problem with the STL I downloaded from thingiverse and thus it does not export well. I tried very quickly to fix the stl with meshlab but did not succeed. Anyhow this part is a hack, we should make a nice one using OpenScad only, see repo/hardware/specific_frames/foo for example downloaded from thingiverse.

Notes:

• The 4dof robot might not be perfect yet, collisions might happen when the arm is "folded". But it will do for a first test. [EDIT: the v2 I sent should fix that problem! print both anyway]
• For now poppy-4dof-arm-mini is uglily added in the poppy-ergo-jr repo, should be moved to a separate repo. It requires all the submodules from poppy-ergo-jr.