Updated installation guide for Bitshares REST API

https://github.com/oxarbitrage/bitshares-python-api-backend

The installation of the bitshares API that serves the open-explorer.io and other applications is not an easy task. It need several steps and requirements to be installed to finally reach a decent production environment.

The new guide attempts to make this task easier, even if it still a lot of steps, information is more clear than before, a step forward in professionalizing the software.

There is a lot to do in this project, specifically i have plans for this API to support all the calls that the bitshares-core provides making it what can be called a full featured API backend.

Another step forward will be the addition of docker documentation that automates all this steps. A lot of work still to be done.