Figured Bass: Fix layout of non-conformant items

F.B. items which did not follow a proper format were laid out wrongly and with wrong bbox. Fixed (hopefully...).

(note: as a form of latitude, anomalous items ARE accepted by the F.B. system; nut they are not formatted according to F.B. conventions)
Merge pull request #438 from mgavioli/FigBass_fix_layout_of_non-conformant_items

Figured Bass: Fix layout of non-conformant items