Add reference to external sphere model ensemble files

[tomgoddard]

Would like IHM to be able to reference sphere model ensemble files that are too big to be put into the IHM file. Currently the nup84 has such ensembles in the DOI zip archive in PDB format and I hacked references to those files into the nup84 ChimeraX demo by adding a file reference in the ihm_model_list table as follows.

_ihm_model_list.ordinal_id
_ihm_model_list.model_id
_ihm_model_list.model_name
_ihm_model_list.model_group_id
_ihm_model_list.model_group_name
_ihm_model_list.assembly_id
_ihm_model_list.protocol_id
_ihm_model_list.file
1 1 'Cluster 1 best score' 1 'Cluster 1' 1 1 .
2 2 'Cluster 2 best score' 2 'Cluster 2' 1 1 .
3 3 'Cluster 1 ensemble' 1 'Cluster 1' 1 1 extra_data/ensembles/cluster1.pdb
4 4 'Cluster 2 ensemble' 2 'Cluster 2' 1 1 extra_data/ensembles/cluster2.pdb

Instead the link out should be an id to another table that lists all the externally linked files either by DOI+archive path, URL, or local file path. That table would also list the file format -- for instance the sphere model ensembles might be in RMF format (currently used by IMP) or a binary trajectory format.

[tomgoddard]

Duplicate of #12.