remove _cache_paths (path is now directly in option)

better TiramisuAPI support

tiramisu/setting.py

@@ -175,7 +175,6 @@ class ConfigBag:
                  'permissives',  # permissives for current context
                 )
     def __init__(self, context, **kwargs):
-        #self.force_permissive = False
         self.context = context
         for key, value in kwargs.items():
             setattr(self, key, value)
@@ -196,10 +195,17 @@ class ConfigBag:
         self.properties = frozenset(self.properties | {'permissive'})
 
     def __delattr__(self, key):
-        if key == 'properties':
+        if key in ['properties', 'permissives']:
+            try:
+                super().__delattr__(key)
+            except AttributeError:
+                pass
             return
         raise KeyError('unknown key {} for ConfigBag'.format(key))
 
+    #def __setattr__(self, key, value):
+    #    super().__setattr__(key, value)
+
     def copy(self):
         kwargs = {}
         for key in self.__slots__: