Add user manual

[robo9k]

A user manual is required, explaining how to:

• download (which version Implement versioning #2 etc.)
• compile (software dependencies, configuration options etc.)
• install (user permissions, options etc.)
• configure (logging etc.)
• run (config file, enviroment variables etc.)
• use as a library from Python, C, Cython etc. (Add usage examples #3)

The manual should also mention that q3py is targeted at developers, not gamers or server admins.

The manual should be part of the README, the documentation and possibly in a GitHub wiki page as well.

[robo9k]

Most of those are explained in the documentation, still needs to be expanded somewhat.
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