Add jexl links for linkout service to tracks

[ctcncgr]

The formatDetails attribute of the jbrowse2 track config can be used to set linkouts for the gene details panel in jbrowse2. We should add this and figure out how we want to generate linkouts in jbrowse2.

This is currently done at:

https://cicer.legumeinfo.org/tools/jbrowse2/

Example with hardcoded refs from the link above:

"formatDetails": {
    "feature": "jexl:{GCV:'<a href=https://cicer.legumeinfo.org/tools/gcv/gene;cicer='+feature.id+'>'+feature.name+'</a>',Intermine:'<a href=https://lis.ncgr.org/cicermine/gene:'+feature.id+'>'+feature.name+'</a>',Phylotree:'<a href=https://funnotate.legumeinfo.org/?family='+feature.genefamily+'>'+feature.genefamily+'</a>'}"
}

Concept example using components from our kit (this needs to be discussed more):

"formatDetails": {
    "feature": "jexl:{Linkouts:'<a class=uk-button uk-button-default href=#modal-linkout uk-toggle>Linkouts</a><lis-modal-element modalId=modal-linkout><lis-linkout-search-element linkoutQuery='+feature.name+'></lis-linkout-search-element></lis-modal-element>'}"
}