Update templates\samples\tests to use ensure viewstart.cshtml and views directory names are cased appropriately #1559

@pranavkm , could you please review this PR??
nits:
- place the new information in a new paragraph.  it doesn't relate to the example.
- `The template should be located` -> `Custom templates are found`
- better to say `a <c>DisplayTemplates</c> folder` because there isn't just one: there could be multiple folders with this name per-controller as well as under `<c>Shared</c>`.
- last sentence is a bit confusing.  suggest `The folder name is case-sensitive on case-sensitive file systems.` or (more technically correct but perhaps to wordy) `Checks for these folders are case-sensitive on case-sensitive file systems.`