list= is an optional parameter, reflected this in the Maybe type.

* uses scripts in ./nix/ to generate packages.json and purs-packages.nix
* build-purs now builds with dependencies in nix store
* PURS_IDE_SOURCES set in nix shell, so those are directly usable from latest versions of purescript-langauge-server and psc-ide-emacs
* regular psc-package usage is still supported

Merge branch 'dev-doc-table-optimization' of ssh://gitlab.iscpif.fr:20022/gargantext/purescript-gargantext into dev-merge

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

Merge branch 'issue184' of ssh://gitlab.iscpif.fr:20022/gargantext/purescript-gargantext into dev-merge