Annotation performance needs tweaking

[jvlasblom]

Need to test with profiler and optimize annotator for all sizes of VCFs. (Small VCFs with variants widely spaced can be slow to annotate depending on how parameters are set).

[jvlasblom]

Another way to improve performance on batches of VCFs would be to process all the VCFs at once instead of serially, so that within a certain region on the chromosome there will be many densely packed variants from the various VCFs. By increasing the density in this way, we will require fewer tabix seeks.