Fix/sharing dialog props and data table contect menu initial position

[HendrikThePendric]

These are two unrelated fixes:

1. The SharingDialog would open OK from componentDidMount, but when called from componentWillReceiveProps it would be working with the old props which were about to be replaced. Now passing the props as parameters to loadObjectFromApi and using nextProps in componentWillReceiveProps.
2. When using React 16 and MaterialUI 0.19+ The DataTableContextMenu would initially render briefly in the top-left. Fixes with some CSS rules suggested int he issue thread [Popover] Positioning delayed mui/material-ui#8040 and Eduardo's fix in the dashboard app.

[varl]

LGTM