Added modular DAL, updated gluon imports to new structure

gluon/dal/_globals.py

@@ -0,0 +1,13 @@
+import threading
+import logging
+
+GLOBAL_LOCKER = threading.RLock()
+THREAD_LOCAL = threading.local()
+
+LOGGER = logging.getLogger("web2py.dal")
+
+DEFAULT = lambda: None
+
+def IDENTITY(x): return x
+def OR(a,b): return a|b
+def AND(a,b): return a&b