Update EAF lower limit field in new standard

[ljwh2]

Effect allele lower limit does not make sense for sumstats where EA=ALT, since it is minor allele frequency that needs masking, not ALT allele frequency - ALT is not necessarily the minor allele. A better solution would be to change the field to "effect allele frequency reported range". Permitted values would need to include range and <> (e.g. 0.1-0.9, >0.1). Or, if easier >0.1 could be expressed as 0.1-1.

See discussion on slack 2nd Feb.

[jdhayhurst]

• changed effectAlleleFreqLowerLimit to minorAlleleFreqLowerLimit
• changed missing value repr from NA to #NA
• added coordinateSystem (1-based/0-based) to the metadata model