Refactor attester as a module

Refactor the command line interface moving the parameters parsing to the bin file.

Any parameter passed to the command line is now also available in attester configuration `globals` property.

This allows to configure parameters like `port` and `log-level` from the configuration file.
Values passed to the command line are still overriding the ones defined in the file.

This is a first step in the evolution of attester because it removes any `cli` information from the main attester module.