Renaming SourceGrammar to Grammar and similarly for some related types

Included renamings:

	SourceGrammar -> Grammar
	SourceModule -> Module
	SourceModInfo -> ModuleInfo
	emptySourceGrammar -> emptyGrammar

Also introduces a type synonym (which might be good to turn into a newtype):

	type ModuleName = Ident

The reason is to make types like the following more self documenting:

	type Module = (ModuleName,ModuleInfo)
	type QIdent = (ModuleName,Ident)

src/compiler/GF/Interactive.hs

@@ -153,7 +153,7 @@ execute1 opts gfenv0 s0 =
     continue = return . Just
     stop = return Nothing
     env = commandenv gfenv0
-    sgr = sourcegrammar gfenv0
+    sgr = grammar gfenv0
     gfenv = gfenv0 {history = s0 : history gfenv0}
     pwords s = case words s of
                  w:ws -> getCommandOp w :ws
@@ -280,7 +280,7 @@ execute1 opts gfenv0 s0 =
          continue gfenv'
 
     empty = continue $ gfenv {
-              commandenv=emptyCommandEnv, sourcegrammar = emptySourceGrammar
+              commandenv=emptyCommandEnv, grammar = emptyGrammar
              }
 
     define_command (f:ws) =
@@ -355,8 +355,8 @@ fetchCommand gfenv = do
 importInEnv :: GFEnv -> Options -> [FilePath] -> SIO GFEnv
 importInEnv gfenv opts files
     | flag optRetainResource opts =
-        do src <- importSource (sourcegrammar gfenv) opts files
-           return $ gfenv {sourcegrammar = src}
+        do src <- importSource (grammar gfenv) opts files
+           return $ gfenv {grammar = src}
     | otherwise =
         do let opts' = addOptions (setOptimization OptCSE False) opts
                pgf0 = multigrammar (commandenv gfenv)
@@ -398,14 +398,14 @@ prompt env
     abs = abstractName (multigrammar env)
 
 data GFEnv = GFEnv {
-  sourcegrammar :: SourceGrammar, -- gfo grammar -retain
+  grammar :: Grammar, -- gfo grammar -retain
   commandenv :: CommandEnv,
   history    :: [String]
   }
 
 emptyGFEnv :: GFEnv
 emptyGFEnv =
-  GFEnv emptySourceGrammar (mkCommandEnv emptyPGF) [] {-0-}
+  GFEnv emptyGrammar (mkCommandEnv emptyPGF) [] {-0-}
 
 wordCompletion gfenv (left,right) = do
   case wc_type (reverse left) of