Also, some test refactoring and add servant-client to tests.

Get rid of that TVar completely.

Also, some fixes to NodeStory (it inserts ngrams when saving node
story, when they don't exist).

Basically, Gargantext.Prelude exports all of Protolude now.

This big commit improves the jobs API in a way that now we can
completely abstract away over a JobLog.

This is used to save when quitting the server. Previous, debounce
save, didn't work properly on exit.