Improve authentication dialog

We weren't telling the user what they were logging in to.

Also, asking for a server first is more user-friendly.
Add docstrings for api's report.py
Improve report selection UI
Add license
Improve setup.py
Improve style and docs
Improve interface's session

It's better to ask the user for the server information first. Also,
we give the user a message about what is happening instead of just
asking them for their username and password.
Replace README.rst with DESCRIPTION.rst
Improve style and formatting
Merge documentation updates into master

Conflicts:
	nessusinterface/session.py

Conflict resolved by using newer changes