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/Abstract.hs

@@ -43,14 +43,20 @@ valIntOpts flag def opts =
 
 valStrOpts :: String -> String -> [Option] -> String
 valStrOpts flag def opts =
-  case [v | OFlag f v <- opts, f == flag] of
-    (VStr v:_) -> v
-    (VId  v:_) -> v
-    (VInt v:_) -> show v
-    _          -> def
+  case listFlags flag opts of
+    v:_ -> valueString v
+    _   -> def
+
+listFlags flag opts = [v | OFlag f v <- opts, f == flag]
+
+valueString v =
+  case v of
+    VStr v -> v
+    VId  v -> v
+    VInt v -> show v
 
 isOpt :: String -> [Option] -> Bool
-isOpt o opts = elem o [x | OOpt x <- opts]
+isOpt o opts = elem (OOpt o) opts
 
 isFlag :: String -> [Option] -> Bool
 isFlag o opts = elem o [x | OFlag x _ <- opts]