This reverts commit f4284b4e.

This reverts commit efbe327f, reversing
changes made to 6d9bcd07.

We have contexts.hash_id which is enough (computed by postgres as a
trigger).

Basically, Gargantext.Prelude exports all of Protolude now.

This fixes commit 5d5300cd which
automatically changed all 'return' to 'pure' in our code, resulting in
broken SQL etc.

This commit refactors the codebase to add a new function called
`addDocumentsToHyperCorpus` which generalises the common pattern of
calling `insertMasterDocs` and later adding the documents via the DB
`Doc` functions.

It also "lowers" some functions to run into a plain `DBCmd`.

One issue is that it creates new list/docs/board/graph nodes.

This turned out to be quite heavy because of module import cycles.