Table: add draggable rows

[mcarrano]

Add draggable row capability to Table as a follow up to: patternfly/patternfly#4065 This feature may be added to the composable table if that seems like the best approach.

cc @jessiehuff accessibility considerations here?

[jessiehuff]

I imagine that this would follow similar accessibility considerations as the draggable datalist component that we implemented with this PR. We might need to make adjustments when considering for table though that we can determine if implementation issues come up.

[mcoker]

@nicolethoen @kmcfaul the core work has been merged - patternfly/patternfly#4120

• Creates a td.pf-c-table__draggable for the draggable button
• .pf-c-button.pf-m-plain goes in td.pf-c-table__draggable
• Adds .pf-m-ghost-row to the parent tr when dragging
• Same a11y as the draggable data-list - documented under the draggable table example in core