Topological group uniformities. Roelcke uniformity.

[dan323]

Proof that the Roelcke uniformity is a uniformity, defined in here for example.

• [x] Define a the Roelcke uniformity
• [x] Add a proof that it is indeed a uniformity
• [ ] Add a proof that muliplication and inverse functions are uniformly continuous

[dan323]

For the 3rd step, we need this issue

[SKolodynski]

Uniform continuity of the inverse is done with inv_uniform_roelcke, what still remains to be done is the uniform continuity of the group operation.