Add ability for adapters to supply a ReactComponent that helps load itself

[cmdcolin]

Adapters can sometimes have special logic that is needed to instantiate them that goes beyond the simple "file+index" guess adapter method

As an alternative, we could let the adapter provide a reactcomponent that contains form elements that help instantiate a particular adapter type

This will be especially helpful for synteny tracks which can require assembly names and file(s) to be loaded at once

Then, things like the DotplotImportForm can loop over all the "SyntenyAdapters" (this is a new concept as well, a group of adapter types might be called SyntenyAdapters) and provide put their ReactComponent inside the import form

Perhaps also, the Add track widget can provide access to these ReactComponents too

[cmdcolin]

the customized "add track workflows" can help with this I think

[cmdcolin]

could possibly keep this open but it's no longer "impossible" to have custom add track workflows

[cmdcolin]

the custom add track workflows may be sufficient for this