Smart push

The main goal of this merge request is to properly implement pushing to the platform.

Until now, only the object selected was pushed which could end up badly as no version nor fork check was done.

Also, new object push was not tested and, in fact, that part never worked.

This merge request fixes several issues related to that:

1. Fixes push of newly created data
2. Push all dependencies of an object prior to the object itself
3. Centralize the push command as it was the same everywhere
4. Refactor the WebAPI class to make it clean and use the requests package
5. Refactor tests so that the WebAPI class is also used there and is therefore also tested
6. Add missing tests for the library asset

Fixes #49 (closed) #50 (closed)