modbvbar and modbhbar format

[Zaher Salman]

It would be nice to add data-format option to modbvbar/modbhbar. For example by changing

mvalue = mie_to_string(tid, value);

with

mvalue = mie_to_string(tid, value, modbhbar[i].dataset.format);

[Stefan Ritt]

Implemented in current version and added to documentation.