fix #1355 update SynEvents browser detection

The SynEvents util had an obsolete browser detection.
It has been removed and the `aria.core.Browser` one is used.

close #1355 and #1356
fix Messages in ErrorListWidget were inevitably escaped.

Now there is an option in the messages objects passed to the widget which controls how the message is escaped when displayed by the template.

Closes #1357
fix #1349 aria.utils.dragdrop.Drag on Chrome with elements in position:fixed

This commit fixes a problem inside the getOffset method of the aria.utils.Dom class. We use the offsetParent property to compute the element position, but for a fixed element in Chrome the offsetParent is null and it breaks the code.