Support Vue router props in CDropdownItem / Link

[joel-wenzel]

Currently CDDropdownItem only supports href prop. It would be nice if the Vue Router object props were also supported.

New Props:

• to: supports string path or Vue Router Location object
• nuxt: not as critical as "to" but would be nice to add also. A simple boolean prop that embeds a NuxtLink

CDDropdownItem currently extends CLink so it would be nice to implement this logic in CLink so it could be shared by all linkable components.

I can create a PR for this if you are ok with the feature.