Integrated JBrowse with dynamic fasta and bam track loading

Integrated JBrowse; data selector above the browser allowes you to browse projects and data tracks. Clicking on the track in the list displays it in the genome browser. 
If the track selected is fasta track, all tracks are removed to assure coordinate system consistency (effectively meaning only one fasta track can be present per browser instance; this is JBrowse limitation).  

Information on setup (how to use changes to Vagrantfile and base.py and how to prepare sequences) are available in the readme.

Why defining empty preFilter?