Matias Guijarro authored Jul 29, 2019 and Sebastien Petitdemange committed Aug 20, 2019

In order to make it nicer for users, the global objects are initialized
in bliss/__init__.py ; leaking module-level globals from imports are
made 'private' with '_' (do not show)
The logging_startup function is moved from logtools to __init__.py as
well.

Aliases refactoring:
* removed AliasMixin class
* removed 'alias_or_fullname, alias_or_name properties
    - code explicitely ask for name, fullname or alias instead
* only objects found in env dict can be aliased, or counters
    - the CounterWrapper object is a proxy that evaluates to the corresponding
      counter at runtime, in order to make sure the alias is always in sync
      with the counter. The proxy code is a modified version of the proxy
      from the 'wrapt' project, from 'lazy-object-proxy' (PyPI)
* added set() and remove()