Refactorization of zowi parts

[Obijuan]

Zowi parts can be implemented easily using sketches and clones. It will make it easier for the people to change the parts and create derivative designs.

[Obijuan]

The leg part has been already refactored. I am working in my fork. When every part is finished, printed and tested I will merge into zowi's master

Leg parts has not been printed nor tested yet