Component - Nav Dropdown

[priley86]

• We will need to enhance React Bootstrap's NavDropdown to support Patternfly style navs w/ icons. We also need to review all Nav styles built by React Bootstrap in the masthead.

This was noted during development of the PF-R Demo App:
https://github.com/patternfly/patternfly-react-demo-app

[priley86]

This PF3 issue is stale and no longer being actively worked. Closing this for now. Will reopen if we determine it is needed later.