Get rid of AF service, replacing AF 1000G with 5 population 1000G AFs.

[tonydisera]

I've added population allele frequencies for 1000G to the tooltip.

Now we need to decided if we want to remove the AF service from IOBIO. The issue is that gnomAD allele frequencies are not yet provided for GRCh38.

[tonydisera]

We can only get rid of the AF service when a) VEP support all gnomAD allele frequencies (including whole genomes) and b) GRCh38 is supported in gnomAD (and VEP)