I moved HasConfig to Core/Config instead of it being in Database.Prelude

This commit moves `GargConfig` and the other config-related
data structures back into gargantext, so that they can be edited
and expanded without needing to worry about the prelude project.

Basically, Gargantext.Prelude exports all of Protolude now.

This important commit introduces the 'DbCmd' constraint set, allowing DB
functions to require only a connection pool and some `GargConfig`.

NOTE: This doesn't compile yet because of HTML types.

The ui_cwTouchMail is not used, it should be removed in the future.