Add support for searching among WGS variant call results

[Nicklas Nordborg]

This should be relatively easy to fix since it is more or less compatible with the filtered variant calls from the RNAseq pipeline. The main difference is that the VCF files have results for both the normal and tumor samples.

[Nicklas Nordborg]

In 7668:

References #1584: Add support for searching among WGS variant call results

Added an item list and index definition for the paired WGS variant calls. It seems to work if we select the second (tumor) column when indexing.

[Nicklas Nordborg]

In 7669:

References #1584: Add support for searching among WGS variant call results

Implemented a "sample filter" functionality in VcfFile and VcfFileLocator interfaces so that it is possible to specify which sample column to use when parsing the VCF.

[Nicklas Nordborg]

In 7670:

References #1584: Add support for searching among WGS variant call results

If the genotype is phased we need to replace '|' with '/' to make it compatible with other indexes.

[Nicklas Nordborg]

In 7671:

References #1584: Add support for searching among WGS variant call results

Some changes to column widts that should work better in some cases where the number of hits is large.