Reorganize module namespace

- Remove Language.Haskell prefix from all modules
- Move 'GHCMod.*' to 'GhcMod.Exe'
- Move 'GhcModExe' to 'GhcMod.Exe'

test/PathsAndFilesSpec.hs

@@ -1,9 +1,9 @@
 module PathsAndFilesSpec where
 
 
-import Language.Haskell.GhcMod.PathsAndFiles
-import Language.Haskell.GhcMod.Cradle
-import qualified Language.Haskell.GhcMod.Utils as U
+import GhcMod.PathsAndFiles
+import GhcMod.Cradle
+import qualified GhcMod.Utils as U
 
 import Control.Monad.Trans.Maybe
 import System.Directory