Demonstrate #1485, #1487, #2662, #2664 in functional and unit tests

[dougbu]

• test additional cases close to these bugs as well

for #1485

• show odd @Html.CheckBox(), @Html.Hidden() behaviour in unit tests
• show odd @Html.TextBox() behaviour in functional tests (templates)

for #1487

• show odd @Html.Value() behaviour in unit tests
• show odd @Html.RadioButton(), @Html.TextArea() behaviour in functional tests
• show lack of validation attributes for @Html.RadioButton(), <select> tag helper

for #2662

• show odd @Html.RadioButton(string.Empty) behaviour in functional tests

for #2664

• show failures with @Html.ListBox() in unit tests

nits:

• test IHtmlHelper methods, not extensions
• use ViewData, not ViewBag in HtmlGeneration_FormController
• name test methods a bit more consistently
• rename HtmlHelperValueExtensionsTest to HtmlHelperValueTest

[dougbu]

/cc @Eilon let's discuss tomorrow and decide if the expectations in the skipped tests match what we want.

[dougbu]

Will reopen with correct base bracn