[BUG] - Format EF as Personnummer

[Johannestegner]

Context

Enskild Firma should make use of the + separator in formatting if the firma/owner is above 100 years old.

The following snippet should be changed:

    public String format(boolean separator) {
        String nr = this.getShortString();

        return separator ?
                nr.substring(0, 6) + "-" + nr.substring(6) :
                nr;
    }

Expected outcome

EF's with age over 100 should contain the + separator if separator param is true.

Actual outcome

EF's with age over 100 contains the - separator if separator param is true.

For more context, see: organisationsnummer/csharp#38