Provide documentation in github wiki

[oevans]

The inline syntax comments are helpful to learn specific functions, but I believe it would be much more user-friendly to provide the documentation in a wiki format now that PortalPy is on Github. Having a wiki with a master list of function names as hyperlinks to specific syntax pages about each function would make it much easier to learn PortalPy and navigate the documentation.

To avoid having to maintain documentation in two locations I would be in favor of removing the comments from each function in the code files and having the wiki be the main source.