This is achieved by introducing graph Stage. We can split initial
rendering then from hooks when ready (like showing marked selections)
and the cleanup stuff.

useAff cached to aggressively. Added refs for path comparison (this also
adds a requirement of Eq path to useLoader now).

Also, removed lots of duplicated code in Loader.purs and unified to have
only one loader.

Merge branch 'dev-contact' of ssh://gitlab.iscpif.fr:20022/gargantext/purescript-gargantext into dev-contact

Merge branch 'dev-contact' of ssh://gitlab.iscpif.fr:20022/gargantext/purescript-gargantext into dev-contact

useMemo in useLoader does shallow object comparison -- probably this is
the reason.

Merge branch 'dev-graph-eff-rewrite' of ssh://gitlab.iscpif.fr:20022/gargantext/purescript-gargantext into dev

Merge branch 'dev-forest' of ssh://gitlab.iscpif.fr:20022/gargantext/purescript-gargantext into dev-forest

Remove utility functions. They were reading refs constantly, pattern
matching on Maybe/Either. We can do everything in one go.