fix #452 MouseEvent.pageX/Y not supported in Firefox 3.6 (FireDomEvent)

Since e4e3296618f13aa307a7acc4e9a452381f003985, multiple test cases
were failing in Firefox 3.6 due to the bug in the browser where
an error was thrown when trying to override pageX/pageY of a custom
event. This commit adds a workaround for that bug.
fix #454 can not select options in AutoComplete

In b88bc5173c227746af98dc6fab20f58235f8c164, deprecated usage of expandos
was removed from DomElementWrapper, but it was still used in the TPL code
and due to it, options could not be selected in AutoComplete.
fix #455 DatePicker maxValue unselectable

After 4e030c64fa76a13139f9ada0180a89446c8fbd4f, the day specified as
maxValue date in CalendarController config might have been unselectable.
doc Fix link in release notes template
fix #458 error when no skin and no widgets loaded

Due to a bug in the code delivered in 59e9ba72a65c810df7935c5a1a4195365e44d233
(pull request #427), when no skin and no widgets were loaded, JavaScript
errors were thrown due to nullpointer exception.
refactor Two new features have been added in the LayoutTester:

  - The elements positionning are now relative to the root element (default to body)
  - An error margin can be given for more stable tests

Moreover, some vertical alignement tests have been added.

Close #457
1.4.1