Restricted: Allow datetime module class attributes.
    
To allow the class attributes, we add a helper method ``allow_class_attribute''.
 Why addng this is because allow_module can allow instance methods but not class
 attributes.
 For example, datetime.datetime.now(), datetime.datetime.max, dict.fromkeys(),
 Decimal.from_float(), epoll.fromfd(), itertools.chain.from_iterable() are class
 attributes in Python 2.7.
    
 Also, add a special in-advance-import for datetime.datetime.strptime().
 It is because datetime.datetime.strptime() imports _strptime by C function
 PyImport_Import which calls
 __import__(name, globals, locals, fromlist=['__doc__'], level=0).
 The "level=0" is not supported by AccessControl in Zope2. At the same time,
 the dummy from '__doc__'  is neither allowed in it by default.
 Therefore we import _strptime in advance in this monkey patch file.
 This prevents both importing _strptime with level=0, and accessing __doc__,
 when calling datetime.datetime.strptime() in Restricted environment.

/cc @vpelletier @jm @klaus

/reviewed-on nexedi/erp5!275

erp5_officejs_support_request_ui: Check the "Empty Criterion is Valid" checkbox in "Unsafe" web section.

Without check the "Empty Criterion is Valid", the web section will return nothing. But due to a bug, the web section will return all documents anyway. This should be checked.

Rename `rjs_gadget_erp5_pt_listpage*` to `gadget_supportrequest_pt_listpage*`.
Rename `rjs_gadget_erp5_pt_form_view_discussable*` to `gadget_supportrequest_pt_form_view_discussable*`.

Web pages which ID starts by `rjs_gaget_erp5` will be include in `erp5_web_renderjs_ui` bt5. We want the custom page template only be included in the `erp5_officejs_support_request_ui`.

Rename the title of left chart to "Support Requests Pipe", right chart to "Last Month Activity"

And replace devellopement by app in titles

ECharts has better visual effect than Chartjs.
And also update the tests.