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

@pranavkm , could you please review this PR??
- nit: non-extension method here would be `Editor(expression: string.Empty, templateName: string.Empty, htmlFieldName: null, additionalViewData: null)`
- why pass `string.Empty` template name?  just use `null`