LP1835982 Grid cell print values option

LP1835982 Grid cell print values option

Allow grid callers to implement functions that return plain text
(printable) values for a given cell.  These are primarily useful when a
cell is rendered via cellTemplate, which may not produce content which
is ideal for printing. Such functions are specified by the cellPrintValue
attribute in the eg-grid-column element.

Includes sample implementation for the Angular record detail copies
grid, which uses several cellTemplate cells.

Signed-off-by: Bill Erickson <berickxx@gmail.com>
Signed-off-by: Galen Charlton <gmc@equinoxinitiative.org>