provide the number of worked multis separately per band

[ftl]

• Provide the number of worked multis separately per band. Use conval.Counter.MultiProperties() and conval.Counter.MultisPerBand(property, band) to find out the numbers.

• Add one column per multi to the score table (for example dxcc_entity and itu_zone instead of just multis) in the score window.

• Add one column accordingliy to the score table in the summary file.