Comment out some dead code found with -fwarn-unused-binds

Also fixed some warnings and tightened some imports

src/compiler/GF/Command/Interpreter.hs

@@ -9,7 +9,6 @@ import GF.Command.Parse
 import PGF.Internal(Expr(..))
 import GF.Infra.UseIO(putStrLnE)
 
-import GF.Text.Pretty(render)
 import Control.Monad(when)
 import qualified Data.Map as Map
 

src/compiler/GF/Command/TreeOperations.hs

@@ -4,7 +4,7 @@ module GF.Command.TreeOperations (
   treeChunks
   ) where
 
-import PGF
+import PGF(PGF,CId,compute,unApp,paraphrase)
 import PGF.Internal(Expr(..),unAppForm)
 import Data.List