Auto add 0 when making a single digit number subparagraph

[Tmpecho]

When adding a new paragraph in "lovverk", if you for example write 13.1, since it expects a two digit number after the period, it creates a new subparagraph 13.10 instead of 13.01. So if a single digit number is written after the period, add a zero digit in front of it.

Also for frontend, you shouldn't be able to enter non numeric or period symbols into the paragraph number field.