documentation improvements; higher level Mongodb wrapper

tests/compile/tmongo.nim

@@ -0,0 +1,16 @@
+
+import mongo, db_mongo, oids, json
+
+var conn = db_mongo.open()
+
+var data = %{"a": %13, "b": %"my string value", 
+             "inner": %{"i": %71} }
+
+var id = insertID(conn, "test.test", data)
+
+for v in find(conn, "test.test", "this.a == 13"):
+  print v
+
+delete(conn, "test.test", id)
+
+close(conn)