Adding "dropright"/"dropleft" prop to Dropdown component

[DhawalRank-zz]

Issue description

• components: Dropdown
• reactstrap version: 4.8.0
• import method 'reactstrap/DropDown';
• react version 16.2.0
• bootstrap version 4

What is happening?

Nesting a dropdown into another dropdown

What should be happening?

There should be a prop option "drop" right as provided by bootstrap as a class named "dropright" to open the dropdown menu on the right of the dropdown button

[TheSharpieOne]

The DropdownMenu has a prop right which accepts a boolean to indicate whether or not the menu should open to the right.
See the Alignment section of https://reactstrap.github.io/components/dropdowns/

Nevermind, I see, they added something new: http://getbootstrap.com/docs/4.0/components/dropdowns/#dropright-variation

[flippidippi]

Just ran into this also. Should we create a new issue with subtasks to get reactstrap caught up with the official release?

[TheSharpieOne]

We can just use individual issues and add them to the same milestone or project to group them together.

[supergibbs]

Instead of adding more props I deprecated dropup and replaced with direction. You can set direction to "down" (default), "up", "left" or "right". Is still backwards compatible with dropup IF you don't use direction. See #813