Documentation for Limiting Search Space Option

[pehamTom]

The current documentation doesn't include any information on options regarding limiting search space in the compile method.

I suggest introducing a subsection regarding this topic in the Exact Mapper section in Mapping.rst.

[burgholzer]

@IsFairy could you please take care of this once #114 is merged?

[burgholzer]

@IsFairy. Just pinging here. Would be great to add to the documentation. Probably the cleanest solution would be to add a new Jupyter notebook in the documentation that explains the context and shows off some options with code examples and some illustrations.