Allow models to reference individuals in other models

[kltm]

This is a feature/discussion request for the ability to reference individuals in other models with an eye to reduce repetition and aid in giving context for model meaning without creating more work.

From discussion with @goodb

[kltm]

Things to think about are:

• where might evidence be stored
• should these be by curation group to prevent incidences of accidentally changing out-group models?
• shadow nodes and event dropping?
• more to discuss

[goodb]

For example, see 'canonical wnt using companions' http://noctua.berkeleybop.org/editor/graph/gomodel:596ef51500000088# . which contains two function nodes enabled by CTNNB1 . These nodes are purposefully not viewed by curators as 'part_of' the Canonical Wnt Signaling pathway (they are more part of the negative regulation of this pathway), but its important to be able to see them in the model. It would be useful to be able to include elements of other models like these. Either by reference ('megamodel view', no duplication, more challenging editor functions) or by search, copy and add to model.

See also models that refer to sub-models like: http://noctua-dev.berkeleybop.org/editor/graph/gomodel:-42025566