Allow default pre-characters for texts that don't count in character count

The 160-character texts are archaic but it doesn't look like it's going to budge. Also, sending out from random text numbers that are not identifiable as from the studio makes customers less likely to read the texts. This means we have to use valuable characters identifying ourselves. At least add a default defined identification of the studio name that populates at the beginning of the text and does not count against the character count.