Remove examples directory; these now live in gf-contrib

All changes have been reflected in the gf-contrib repository:
https://github.com/GrammaticalFramework/gf-contrib

Now, for WebSetup to build the example grammars, one must have gf-contrib
cloned in the same top-level directory as GF. When this isn't the case,
WebSetup displays a notice without failing.

WebSetup.hs

@@ -1,12 +1,13 @@
 module WebSetup(buildWeb,installWeb,copyWeb,numJobs,execute) where
 
-import System.Directory(createDirectoryIfMissing,copyFile)
+import System.Directory(createDirectoryIfMissing,copyFile,doesDirectoryExist)
 import System.FilePath((</>),dropExtension)
 import System.Process(rawSystem)
 import System.Exit(ExitCode(..))
 import Distribution.Simple.Setup(BuildFlags(..),Flag(..),CopyDest(..),copyDest)
 import Distribution.Simple.LocalBuildInfo(datadir,buildDir,absoluteInstallDirs)
-import Distribution.Simple.Utils(die)
+import Distribution.Simple.Utils(die,noticeNoWrap)
+import qualified Distribution.Verbosity
 
 {-
    To test the GF web services, the minibar and the grammar editor, use
@@ -16,6 +17,16 @@ import Distribution.Simple.Utils(die)
    Chrome). The example grammars listed below will be available in the minibar.
 -}
 
+{-
+  Update 2018-07-04
+
+  The example grammars have now been removed from the GF repository.
+  This script will look for them in ../gf-contrib and build them from there if possible.
+  If not, the user will be given a message and nothing is build or copied.
+  (Unfortunately cabal install seems to hide all messages from stdout,
+  so users won't see this message unless they check the log.)
+-}
+
 example_grammars =  -- :: [(pgf, subdir, src)]
    [("Letter.pgf","letter",letterSrc)
    ,("Foods.pgf","foods",foodsSrc)
@@ -34,10 +45,20 @@ example_grammars =  -- :: [(pgf, subdir, src)]
     letterSrc = ["Letter"++lang++".gf"|lang<-letterLangs]
     letterLangs = words "Eng Fin Fre Heb Rus Swe"
 
+contrib_dir :: FilePath
+contrib_dir = ".."</>"gf-contrib"
 
-buildWeb gf (flags,pkg,lbi) =
-    do --putStrLn "buildWeb"
-       mapM_ build_pgf example_grammars
+buildWeb gf (flags,pkg,lbi) = do
+  contrib_exists <- doesDirectoryExist contrib_dir
+  if contrib_exists
+  then mapM_ build_pgf example_grammars
+  else noticeNoWrap Distribution.Verbosity.normal $ unlines
+    [ "---"
+    , "Example grammars are no longer included in the main GF repository, but have moved to gf-contrib."
+    , "If you want these example grammars to be built, clone this repository in the same top-level directory as GF:"
+    , "https://github.com/GrammaticalFramework/gf-contrib.git"
+    , "---"
+    ]
   where
     gfo_dir = buildDir lbi </> "examples"
 
@@ -47,7 +68,7 @@ buildWeb gf (flags,pkg,lbi) =
          execute gf args
       where
         tmp_dir = gfo_dir</>subdir
-        dir = "examples"</>subdir
+        dir = contrib_dir</>subdir
         args = numJobs flags++["-make","-s"] -- ,"-optimize-pgf"
                ++["--gfo-dir="++tmp_dir,
                   "--gf-lib-path="++buildDir lbi </> "rgl",
@@ -63,10 +84,13 @@ copyWeb flags = setupWeb dest
              NoFlag -> NoCopyDest
              Flag d -> d
 
-setupWeb dest (pkg,lbi) =
-    do mapM_ (createDirectoryIfMissing True) [grammars_dir,cloud_dir]
-       mapM_ copy_pgf example_grammars
-       copyGFLogo
+setupWeb dest (pkg,lbi) = do
+  mapM_ (createDirectoryIfMissing True) [grammars_dir,cloud_dir]
+  contrib_exists <- doesDirectoryExist contrib_dir
+  if contrib_exists
+  then mapM_ copy_pgf example_grammars
+  else return () -- message already displayed from buildWeb
+  copyGFLogo
   where
     grammars_dir = www_dir </> "grammars"
     cloud_dir = www_dir </> "tmp" -- hmm