Add :ggload command, which loads all `Prelude`s

The previous commit did not work, because GHCi executed the contents of
`.ghci` *before* loading the project.
This commit makes a new command, `:ggload`, available from GHCi when in
the Gargantext project: typing `:ggload` will make available all symbols
from modules named `Prelude` in the Gargantext project.
The name `:ggload` as well as the set of modules to import are still
open to discussion.

.ghci

-import Gargantext.API.Ngrams.Prelude
-import Gargantext.API.Prelude
-import Gargantext.Core.Text.List.Group.Prelude
-import Gargantext.Core.Text.List.Social.Prelude
-import Gargantext.Database.Admin.Types.Hyperdata.Prelude
-import Gargantext.Database.Prelude
-import Gargantext.Database.Query.Prelude
-import Gargantext.Database.Schema.Prelude
+import Prelude
+
+:{
+let preludes = [ "Gargantext.API.Ngrams.Prelude"
+               , "Gargantext.API.Prelude"
+               , "Gargantext.Core.Text.List.Group.Prelude"
+               , "Gargantext.Core.Text.List.Social.Prelude"
+               , "Gargantext.Database.Admin.Types.Hyperdata.Prelude"
+               , "Gargantext.Database.Prelude"
+               , "Gargantext.Database.Query.Prelude"
+               , "Gargantext.Database.Schema.Prelude"
+               ]
+:}
+
+:def ggload const $ pure $ foldMap (\m -> "import " <> m <> "\n") preludes