R1:5c73c169fd31

Rough cut of "Move tasks to column..."

Summary:
Ref T5523. See PHI50. See PHI40. This isn't perfect, but should improve things.

Add a "Move tasks to column..." action to workboards which moves all visible tasks in a column to another column, either on the same board or on a different board.

This is a two-step process so that I don't have to write Javascript, and because I'm not 100% sure this is what users actually want/need. If it sticks, the UI could be refined later.

- The first dialog asks you to…