Allow searching gene names from user opened GFF3 files on web

[cmdcolin]

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On desktop there is the workflow to perform a name index

On web we could add a similar thing, and maybe just make an entire name index in memory instead of creating an "on-disk trix index"

From office hours with @SamCT

[cmdcolin]

there is a need in this case to allow specifying the fields to be indexing similar to desktop