When counting sentences, ignore initial numerotation
When counting sentences, ignore initial numerotation

This occurs specifically when an amendment modifies an amendment-type
sentence, beginning with one of the following text:
" Art. 3. -
" II bis. -
" 3°
" b)

The regex is possibly/probably to be improved, it should be only accurate
in most cases; the edge cases remain to be found and checked.

Issue: #4

Legilibre/SedLex