Fixed :doc: uses in the docs that were not rendering due to an extra space.
Corrected walkthrough path in doc reference.
Added a couple missing language specifiers for the code-block directive and switched a couple 'yaml' specifications to 'jinja' to get proper highlighting.
Fixed several minor misspellings and acronym capitalizations.
Merge pull request #4148 from gdub/docs

Various minor doc fixes and cleanups