Co-authored-by: supermerill <merill@free.fr>
Based on the unfinished idea of @supermerill, defining ExtrusionRole
as a bit mask of ExtrusionRoleModifier.
Because the ExtrusionRole was used for both ExtrusionEntity and
G-code export / G-code viewer, the original ExtrusionRole had to be split
to ExtrusionRole and GCodeExtrusionRole to support bitmask attributes
for the former while keeing a low number of ordinary values for the latter.
