Add rule: Function names should use PascalCase

[KarolKaczmarek]

https://github.com/PowerShell/DscResources/blob/master/StyleGuidelines.md#function-names-should-use-pascalcase-and-follow-noun-verb-convention-if-possible

[Jaykul]

I'm sure the original author meant "follow verb-noun convention" ... why are we linking to a document that didn't even get the basics right?

Since there's already a rule for testing approved verbs, and even one for testing pluralized nouns, this issue/idea is incomplete, at best -- what rule(s) actually still need to be implemented?

@raghushantha Why is this labelled "up-for-grabs" when it's not specified enough for anyone to implement it?