moveColumn doesn't account for non-movable columns at beginning of columns array

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If you have grouping enabled on a grid, moving columns will break when you try to move things to or from the end of the list. This is because a new invisible treeBaseHeader column is prepended to the list of columns, which is classified as a "nonMovableColumn" in the uiGridMoveColumnService.

Given the following example scenario...

• table with 7 columns, including the treeBaseHeader, and the last 3 columns are invisible.
  • with 'Y' meaning a movable column and 'N' non-movable, the columns array looks like [N, Y, Y, Y, N, N, N]
• moving column from position 1 to position 3
  • I'm assuming this should be considered a valid move

...here's where the error occurs in the moveColumn function:

if (originalPosition >= (columns.length - nonMovableColumns) || finalPosition >= (columns.length - nonMovableColumns)) {
    gridUtil.logError('MoveColumn: Invalid values for originalPosition, finalPosition');
    return;
}

That if-statement evaluates to if (1 >= (7 - 4) || 3 >= (7 - 4)). Since 3 >= (7-4), we get a false-positive error.