IdrisDoc cleanups and Haddock additions

I added more Haddock documentation and reduced the codebase of IdrisDoc while making it merge IdrisDoc documentation more robustly.

Instead of depending on consistent info stored in the IdrisDoc file found in IdrisDoc directories, instead it investigates which namespaces actually are represented in the docs/ directory and uses this info to rebuild the index.html file.

Because the IdrisDoc file no longer stores information about documented namespaces (it is no longer needed!) I had to update a test which depended upon this.