Bug 22571: Handle control fields in MMT for conditionals

Bug 22571: Handle control fields in MMT for conditionals

Control fields are not handled correctly by Koha::SimpleMARC when
comparaison (with or without regex) is done.

Which means we did not support something like:
Do something if control field 008 equals or matches "a string"

Test plan:
Create a new MARC modification template and a new action, like:
Add new field 100$a with value "foo bar" if 008 (or any other control
fields) matches (or equals) a regex
Then use the record mofication tool and confirm that the new field is
create if the regex matches 008 of the bib record

Signed-off-by: Mark Tompsett <mtompset@hotmail.com>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>