Add links of UCSC with fixed tracks

[blakesweeney]

UCSC has some very useful tracks for lncRNA, like various types of methylation. We should provide a link from RNAcentral to UCSC for the region in question, but with these tracks active. The idea is to provide a useful default for people interested in lncRNA data. Probably need some help text about what tracks are chosen, what aren't and what else is possible as well.