Generate static JSON to power website modals

[epistrephein]

Website modals content relied on a symbolic link of the subgraphs directory and its turtle files to power the dynamic generation of stages and divergences. This made the process brittle and a little hacky, so we redesigned it using a python script that dumps the subgraphs content into a static JSON file which is then read by the javascript, populating the modals accordingly.

Together with this change, the modals frontend was redesigned a little:

• Removed the flaky divergences tooltip and moved their content below the stage realization description
• The stage title display also the canonical stage it realizes
• The monomyth expression label is shown instead of a generic label
• Stage 1 is preselected when opening a modal of a work
• Right and left arrow keys can be used to navigate the stages forward and backward (when a work has more than 1 journey, arrows move the last moved journey)
• Added box with ontology documentation link