Clean old branches

[Manu343726]

As I said on the biicode blog post during the release, the current implementation via bii_find_boost() is just the last attempt from a long period of testing different approaches.
The same applies to the development workflow described on the README file, based on block templates and generation via simple python scripts.

There are a couple of branches on the repo history that are currently deprecated, reminiscences from that "Ahhhhhh I'm trying everything to make this work!!!!" period of time.