Support for multiproject builds with nix

- Closes #28

common/src/Configuration.hs

@@ -0,0 +1,23 @@
+{-# Language NoImplicitPrelude #-}
+{-# Language DeriveGeneric #-}
+{-# Language DuplicateRecordFields #-}
+module Configuration where
+
+import ClassyPrelude
+import Dhall (Interpret)
+
+data Pg = Pg { username :: Text
+             , password :: Text
+             , host :: Text
+             , database :: Text }
+        deriving (Show, Generic)
+
+newtype Store = Store { path :: Text } deriving (Show, Generic)
+
+data Config = Config { database :: Pg
+                     , store :: Store }
+            deriving (Show, Generic)
+
+instance Interpret Pg
+instance Interpret Store
+instance Interpret Config