AutoGrid column picker sort handler

AutoGrid column picker sort handler

Adds a default sort handler for column picker onSortChange events.  The
handler simply reloads the grid with the new columns and assumes all
columns are fields on the base class.

Also supports a user custom onSortChange handler for more complicated
situations.

Initial grid load now happens after the column picker loads when the
column picker is enabled to sure the grid only loads once on the initial
load.

Signed-off-by: Bill Erickson <berick@esilibrary.com>