Add excel capabilities to the data table

Here's where we're at with this so far:

[x] support formula entry
[x] make it so Copy Column/Table when allowFormulas=true does not include the headers by default..?
[x] make sure right clicking clears the existing selection in a datatable
[x] performance: many columns/rows shouldn't slow down the whole table too much
[x] typing "=" should cause editing to be started in a cell
[x] fix bug where double clicking a cell with another cell already open causes the clicked cell to quickly open for editing and then reclose
[x] clicking the row number should select the whole row
[x] support cell referencing and auto updating on edit
[x] make sure more than A-Z rows work (aka AA, AB etc..)
[x] prevent equivalent formula from updating the undo/redo stack
[x] allow working with a range of cells/columns A:A or A1:A5 5:5
[ ] make sure row addition/deletion updates cell references
[ ] support dollar sign excel capability ($C$1 fixes the column and row to C1 so that drag down does not go on to C2, C3 etc.)
[ ] make sure column drag updates formulas correctly
[ ] support copy/paste of formulas within table
[ ] allow copy and paste of formula/values into/out of excel
[ ] write tests for various use cases
[ ] (stretch goal) support column reorder
[ ] (stretch goal) support adding/inserting columns
[ ] (stretch goal) add dropdown helper for entering formula, aka start typing SU and get SUM auto completed
[ ] (stretch goal) cell highlighting when entering formulas in cells
[x] fix mispositioning of "Add 10 Rows" button when there are a LOT of rows:

TeselaGen / tg-oss