[IMP] [READD] [IMP] tools: mail: have a strict mode for html_sanitizer (not default) with
options before website: without frames, with safe attributes only.
We will have to find a way to use the strict mode when parsing incoming
emails, but not when sending or storing openerp content.

Currently the not strict mode is the default one, to avoid side-effects with
the website.
[IMP] tools: mail: the cleaner, by parsing and serializing the html content,
encapsulatse the whole content inside a div. This means that html fields are
not editor-clean after being sanitized, because a div has been inserted as root
element. Removing this element allows to have snippets that can be dragged,
dropped, or to insert new snippets inside edited html content in html fields.

[IMP] tools: tests: mail: updated a test accordingly