added Facebook grammar from SummerSchool tutorial on best practices for grammar writing

contrib/summerschool/2013/bestPractices/FacebookI.gf

@@ -0,0 +1,29 @@
+incomplete concrete FacebookI of Facebook = 
+       open 
+         Syntax, 
+         Prelude, 
+         LexFacebook 
+     in 
+{
+lincat 
+   SPerson = NP ;
+   Person = NP ;
+   Place = NP ;
+   Page = NP ;
+   Action = S ;
+   Item = NP ;
+
+
+lin 
+SPersonToPerson sperson = sperson ;
+MorePersons sperson person = mkNP and_Conj sperson person ;
+
+PlaceToItem place = place ;
+PageToItem page = page ;
+ActionToItem action = nounFromS action ; 
+
+CheckIn sperson place = mkS pastTense (mkCl sperson (checkIn place)) ;
+BeFriends sperson person = mkS pastTense (mkCl sperson (beFriends person)) ;
+Like sperson item = like sperson item ;
+
+}