Enhance Template Parser Class Writeup in User Guide

Added two additional sections to the writeup: template parser usage notes, and view fragments.
Clarified a couple of "pseudo-variable" references.

Verified sphinx build.
Signed-off-by:James L Parry <jim_parry@bcit.ca>
Fixed the convention violations.

Changed the HTML example formatting to use tabs instead of spaces.
Adjusted line lengths.

Verified sphinx build.
Signed-off-by:James L Parry <jim_parry@bcit.ca>
Fixed the convention violations.

Changed the section/subsection treatment

Verified sphinx build.
Signed-off-by:James L Parry <jim_parry@bcit.ca>
Merge pull request #3365 from jim-parry/userguide/parser

Enhance Template Parser Class Writeup in User Guide