Bug 37513: Add a way for KohaTable to decide if a button should be displayed

Bug 37513: Add a way for KohaTable to decide if a button should be displayed

This patch adds, for the case of object parameters in the actions config
entry for the KohaTable Vue component, a check for a function on the
current row, that will be used to determine if a button needs to be
displayed or not.

It checks for the function to be defined, and uses it for checking
displayability.

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Matt Blenkinsop <matt.blenkinsop@ptfs-europe.com>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>