Adding matching for deletions that have longer representations

[calledit]

This patch fixes an issue that comes from the fact that deletions can have different REF but still be the same rsID:

Example from vcf file:

NC_000003.12 28891307 . CT C 306.593 . AB=0;TYPE=del;technology.ILLUMINA=1 GT:DP:AD:RO:QR:AO:QA:GL 1/1:22:0,14:0:0:14:366:-32.988,-4.21442,0

Same position from dbSNP:
NC_000003.12 28891307 rs34247537 CTTTT C,CT,CTT,CTTT,CTTTTT,CTTTTTT,CTTTTTTT,CTTTTTTTTTTTT . . RS=34247537;dbSNPBuildID=126

Both represent the same deletion but due to the fact that the dbSNP contains other longer deletions dbSNP has to contain a longer slice of the reference. So will not match using SNPSifts earlier matching algorithm. This patch fixes this issue by appending the extended part of the reference ("TTT" in the example case) to the alt and to the REF then comparing again.

Like this:
"CT".concat("TTT") == "CTTTT" && "C".concat("TTT") == "CTTT"