Short access to already loaded files in workflow builder

[VGPReys]

It would be nice to have an easy way to add a reference file in caprieval when this file has already been added in an other module call.

Currently, having 4 caprieval modules in the same workflow requires to manually go to the 4 of them and search for the reference file.

[sverhoeven]

Using a scenario in the haddock3 webapp you only have to give the reference file once.

To implement here is tricky because file input field does not know about other files already uploaded. This would require something similar whats being done when the schema is rewritten with enums for the chains and residues in a uploaded molecule, but harder as pdb parsing was always from global parameters to node parameters. While *_fname parameters can be in any node. We could rewrite schemas of other nodes with a conditional schema to either pick from list or upload.