CONNT-25: Updated documentation:

- Marked Django 1.11.x as the only supported Django version.
- Updated some copyright notices.
- Updated installation and quick-start instructions for use with new
version of Django.
- Removed unneeded warning about pip version.
- Updated instructions to emphasize that 'crispy_forms' must be
included in list of installed applications.
- Added dedicated section for upgrade instructions. Covered some
general principles and upgrade from 0.3.x to 1.0.x.
- Updated release notes.
- Added information about Graphviz being the external dependency.