teach egGridFields how to compile column tempates

teach egGridFields how to compile column tempates

This adds two optional attributes to eg-grid-field:

 compiled: if present, treat the template inside the
           element as a template to be compiled
 handlers: if present, contains an object with a bucket
           of functions (or whatever) that can be invoked
           inside the template as "col.handlers.foo"

Signed-off-by: Galen Charlton <gmc@esilibrary.com>
Signed-off-by: Galen Charlton <gmc@equinoxinitiative.org>