Track highest versions of algorithms encountered

Redirect pages are created that point from a page using the plain name to the highest version page
Refs #9521
Purge category information before parsing document.

Refs #9521
Only insert alias section if one exists.

Refs #9521
Add deprecation message if neccesary

Also regorganised to base to give easier access to algorithm name/version.
Refs #9521
Update style of directives to be more similar to each other.

Refs #9521
Add highestVersion() method to AlgorithmFactory

It provides easy access to the highest version of an algorithm
currently registered.
Refs #9521
Only add Sphinx ref link if algorithm is highest version

Refs #9521
Fix bootstrap navbar size issue.

Also replace logo with cropped version to take up less space.
Refs #9521
Extend our layout class in category not the default.

Refs #9521
Add docs-html target to CMake

Only added if Sphinx can be found.
Refs #9521
Update docs README to include package requirements

Refs #9521
Use reST for the style guide.

Refs #9521