proposal: change the way client notifies server of user selection actions.

Right now, client send an array of selected row index positions. In the case that user holds down shift and selects a large range (can potentially be many thousands of rows) this is an inefficient way to transmit selection. How about the following:

instead of

{
  type: "SET_SELECTION";
  selection: Array<number>;
  vpId: string;
}

we use this

type RangeTuple = [number, number]

{
  type: "SET_SELECTION";
  selection: Array<number | RangeTuple>;
  vpId: string;
}

So where a consecutive range of row index values must be included, we just describe that range with the first and last index using the RangeTuple. We can send any combination of single values and ranges. Select All becomes trivial [[0, rowCount]]

If user makes a complex extended selection, picking out specific rows and ranges of rows, we might see a selection like this

selection: [1,3,6,[8,11],14,[17,35],[50,100]]

which translates to

[1,3,6,8,9,10,11,14,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,50,51,52 .....100]