Update internal column cache when columns are reordered
ColumnPicker: Update reordering handle to interleave the hidden columns (in their last known position) with the grid's current order.
ColumnPicker: Apply column ordering when the picker is being created, rather then when the columns are reordered.
ColumnPicker: Expose a getAllColumns method so consumer can get the column definitions in order, including hidden columns.
ColumnPicker: Update column order when columns are reordered so that getAllColumns is reliable.
Merge pull request #554 from ajpiano/columnpicker-update-column-cache-on-reorder

Update internal column cache when columns are reordered