fix for StorageList and tests added

gluon/storage.py
StorageList had a recursion error (please check the implementation before committing)

gluon/tests*
added the fix_path module to avoid those ugly lines at the beginning of each test file
added tests for gluon.contenttype and test_fileutils
added tests for missing Storage methods

gluon/tests/fix_path.py

@@ -0,0 +1,30 @@
+#!/usr/bin/env python
+# -*- coding: utf-8 -*-
+import os
+import sys
+
+def fix_sys_path(current_path):
+    """
+    logic to have always the correct sys.path
+     '', web2py/gluon, web2py/site-packages, web2py/ ...
+    """
+
+    def add_path_first(path):
+        sys.path = [path] + [p for p in sys.path if (
+            not p == path and not p == (path + '/'))]
+
+    path = os.path.dirname(os.path.abspath(current_path))
+
+    if not os.path.isfile(os.path.join(path,'web2py.py')):
+        i = 0
+        while i<10:
+            i += 1
+            if os.path.exists(os.path.join(path,'web2py.py')):
+                break
+            path = os.path.abspath(os.path.join(path, '..'))
+
+    paths = [path,
+             os.path.abspath(os.path.join(path, 'site-packages')),
+             os.path.abspath(os.path.join(path, 'gluon')),
+             '']
+    [add_path_first(path) for path in paths]