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/test_cache.py

@@ -4,39 +4,11 @@
 """
     Unit tests for gluon.cache
 """
-
-import sys
 import os
 import unittest
+from fix_path import fix_sys_path
 
-
-def fix_sys_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(__file__))
-
-    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]
-
-fix_sys_path()
+fix_sys_path(__file__)
 
 
 from storage import Storage