Add bgzip indexed fasta support and use indexedfasta npm module

[cmdcolin]

• Enables store class deduction from setting only urlTemplate=test.fa.gz in config
• Enables opening the three files, named test.fa.gz, test.fa.gz.fai, and test.fa.gz.gzi in the Open sequence dialog in browser and electron
• Uses the @gmod/indexedfasta module (which incorporates 1.2.1 version of @gmod/bgzf-filehandle) which goes through a similar barrage of tests that @gmod/twobit does
• Produces identical output on volvox sample track tested by just manual inspection and via tests in the indexedfasta module
• Indexed fasta module has checks for the start >= end returning empty, clamping on start and end of chromosome for coordinates

[cmdcolin]

Note that I did not yet replace the unindexed fasta functionality in core jbrowse with the simple unindexed parser in the indexedfasta module. My aim would be to make the indexedfasta module to generate an index on demand for an unindexed fasta GMOD/indexedfasta-js#2

[garrettjstevens]

Hey @cmdcolin, PR is looking mostly good to me, but I did have one question. Should we add the new driver you created to the list of drivers below? I wasn't able to get a fa/fai/gzi track to load via dialog box in the browser, but I think adding it to there would fix it. (Dialog box in electron worked just fine.)

jbrowse/src/JBrowse/View/FileDialog.js

Lines 63 to 75 in 938cd2b

	this._fileTypeDrivers = [
	new BAMDriver(),
	new CRAMDriver(),
	new BigWigDriver(),
	new GFF3Driver(),
	new GTFDriver(),
	new VCFTabixDriver(),
	new VCFTribbleDriver(),
	new BEDTabixDriver(),
	new GFF3TabixDriver(),
	new BEDDriver(),
	new BigBedDriver()
	];

[garrettjstevens]

Actually, come to think of it, should the IndexedFastaDriver be in that list, too?

[cmdcolin]

@garrettjstevens there is a separate dialog for loading files src/JBrowse/View/FastaFileDialog.js

would be interested to know why it isn't working though

[cmdcolin]

actually, note that you would need to use Open sequence and not Open track to get it to work. It's kind of annoying that Open track and Open sequence are so similar, and that it is sort of a silent "failure" if you use Open track instead of Open sequence. let me know if that helps though

Was looking at the wrong dialog box

[garrettjstevens]

Ah shoot, I was looking at Open File instead of Open Sequence. My bad. Maybe in JBrowse2 we can architect things so that distinction is a bit more clear. PR looks good to me.

[cmdcolin]

I guess if theres no qualms I might go ahead and merge soon. I also noted this feedback from a user about jbrowse desktop and created a new issue #1205 but should not necessarily block this PR