* Uses plugin name instead of class name in !help

It is recorded beside the doc at cls.__errname__ so it can be reused.

* linting

* propagate the change

Also added a property "name" on the plugin objects as a new API.

* linting

* test + few corrections.

* Adapted the tests.

* Fixed the naming of the flows too.

* fix for help

* linting

* utils.py cleanup.

I just applied a couple principles:

- This should not be an API of Errbot
- If not used in Errbot, it is removed
- If is it used only once in Errbot, it is moved to the spot where it is
used
- If it is used a couple times in Errbot and doesn't have a natural spot
within the source tree, it stays.

* linting

This allow a clearer view in the log and a better fine grained filtering
of the verbosity.

make errbot work with python2 on case-insensitive file system (for example, macos)

With a reference implementation with the tox backend.

It works, still have very rough edges.

we have the stream callback contract
and a Tee that can stream from one source to multiple destinations