Column drag in partial renderer

[joneit]

For undiscovered reasons, the 'by-cells' grid renderer should not be used when dragging a column. It produces a rendering anomaly wherein an entire column temporarily goes missing.

Proposed solution: Temporarily set it to a different grid renderer during the drag and reset it back afterwards.

[cha777]

Do we have an event for column drag start just like 'fin-column-changed-event' after columns changed in order to change the grid renderer method