Enhance VanillaRenderer customizable class names

[TheZoker]

Fixes #1677

• Change order of classnames for layouts
• Allow customization of the validation class
• Add class to validation element even if no error occurs

[coveralls]

Coverage decreased (-0.03%) to 88.428% when pulling e308a00 on TheZoker:enhance-vanilla-renderer into 569b23b on eclipsesource:master.

[lucas-koehler]

Implementation looks good to me.

Just add the new control.validation style definition to the Styles.md documentation, please :)

[sdirix]

Regarding the error class: I think we should either consistently hard code the error class or make all of them configurable. @lucas-koehler what do you think?

[lucas-koehler]

Regarding the error class: I think we should either consistently hard code the error class or make all of them configurable. @lucas-koehler what do you think?

While we're already at it I think we should make it configurable in all cases. I imagine this could be useful when using some kind of theme. This also needs to be added to the Styles.md doc then :)