Makefile now builds using cabal, taking advantage of cabal's automatic detection of appropriate build flags.

The only thing lost is ./ghci

Speed: make fast used to take 20 seconds here, when rebuilding from
touching Command/Unused.hs. With cabal, it's 29 seconds.

Assistant/WebApp/Notifications.hs

@@ -7,6 +7,12 @@
 
 {-# LANGUAGE CPP, TypeFamilies, QuasiQuotes, MultiParamTypeClasses, TemplateHaskell, OverloadedStrings, RankNTypes #-}
 
+#if defined VERSION_yesod_default
+#if ! MIN_VERSION_yesod_default(1,1,0)
+#define WITH_OLD_YESOD
+#endif
+#endif
+
 module Assistant.WebApp.Notifications where
 
 import Assistant.Common