'ElectreTriCredibility' and 'ElectreTriCCredibility' merged into one
module ('ElectreCredibility') and adapted to 'Vividict' data structure.

Removed 'ElectreIsOutrankingBinary' module since the same results can be
obtained from 'ElectreCredibility' with some cut relation applied to
them.

Fixes in 'common.py' ('get_input_data', 'get_alternatives_comparisons').

Minor fixes (mostly changes in variables' names) in 'common.py',
'ElectreDiscordance' and 'ElectreConcordanceWithInteractions'.