model.py: Call class: aaf property: now including reference allele frequency
model.py: Call class: aaf property: now including reference allele frequency
model.py: Call class: aaf method: better conditions to check if call comes from Gatk, VarScan, etc.
model.py: Record class: get_alternative method added: Returns a new record containing all the information of current record but only for the
        alternative with the selected index
model.py: Record class: get_alternative method added: Returns a new record containing all the information of current record but only for the
        alternative with the selected index
model.py: Record class: get_alternative method added: Returns a new record containing all the information of current record but only for the
        alternative with the selected index
model.py: Call class: aaf method: better conditions to check if call comes from Gatk, VarScan, etc.
model.py: Call class: aaf method: better conditions to check if call comes from Gatk, VarScan, etc.