Add support for file specific configurations

[vsmalladi]

Add support for file specific track configurations for:
bam
bigWig
bigBed
tabixVCF

[vsmalladi]

Use inheritance based off of the basic track type

[vsmalladi]

Preliminary configuration options: http://hgwdev.cse.ucsc.edu/goldenPath/help/trackDb/trackDbHub.html