Solve bookmarking bug: store file input genes in variable with text input genes

[bhavyaac]

Currently, if a user uploads a list of genes as a file to the app, the bookmarking functionality will not store the names of the genes. It would be helpful if, after reading the file, the app stored the list of genes in the input$gene variable (just like it does with text input), so that the gene names can be stored in the bookmark link.

Example link produced after uploading a file:
http://206.167.183.14/braindex/clusters/?_inputs_&gene=null&vln_points=false&plotly[…]eurons%22%5D&pick_ranked=%22Fcer1g%22&region=%22joint_pons%22

(Suggested by Zaza.)