GF shell: source commands (cc, sd, so, ss & dg) can now be used in pipes

These commands are now implemented as regular commands (i.e. using the
CommandInfo data type) in the new module GF.Command.SourceCommands.

The list of commands exported from GF.Command.Commmands now called pgfCommands
instead of allCommands.

The list allCommands of all commands is now assembled
from sourceCommands, pgfCommands, commonCommands and helpCommand in
GF.Interactive.

src/compiler/GF/Command/CommandInfo.hs

@@ -17,6 +17,8 @@ data CommandInfo env = CommandInfo {
   needsTypeCheck :: Bool
   }
 
+mapCommandEnv f c = c { exec = exec c . f }
+
 emptyCommandInfo :: CommandInfo env
 emptyCommandInfo = CommandInfo {
   exec = \_ _ ts -> return $ pipeExprs ts, ----
@@ -33,6 +35,9 @@ emptyCommandInfo = CommandInfo {
 
 class TypeCheckArg env where typeCheckArg :: env -> Expr -> Either Doc Expr
 
+instance TypeCheckArg env => TypeCheckArg (x,env) where
+  typeCheckArg (x,env) = typeCheckArg env
+
 --------------------------------------------------------------------------------
 
 newtype CommandOutput  = Piped {fromPipe :: ([Expr],String)} ---- errors, etc