took vep_fields into CONSTANT for use in both 454 data & vcf data; put vcf data into %exon_data_ref for use in post-vep processing (as used in 454 data-files); adapted vep_location / ref_location comparison to handle insertions where end position < start position; moved counts & errors into separate 'data' hashref in results; completed adaptation of VEP for vcf data-files