Always allow _MARN/_MARNM removal and "Extended surnames" work for male records

[burtek]

Following discussion in #190, I would suggest an option to remove _MARN/_MARNM fields (per entry, from the person edit dialog / person name edit dialog), which would be always available (regardles of sex/gender, of Extended Surnames feature state etc). This would be good for housekeeping reasons, to be able to easily clear the field when migrating to the Additional Names.