[FIX] website: Odoo's social URLs
[FIX] website: typos
[REM] db_manager: remove old dependencies to datejs and timepicker and replace by momentjs
[IMP] website_forum: better implementation of automatic nofollow attribute
on links in forum posts.

This is now done when creating / updating posts instead of updating the display
of the post. This means that old posts may contain nofollow attribute altough
the user has sufficient karma; however it is acceptable compared to the computation
we save by avoiding processing every post to display.
[IMP] ir.attachment : move the fields index_content (from document), mimetype and datas_checksum (from website) to base. In base, the mimetype is computed with the Magic python lib (if installed, else with a custom function using magic number), and the index_content is an implementation of strings unix command. In document, index_content is still computed with the indexer of document module.
[IMP]Export Wizard: Improve code to not remove fields from "Fields to Export"on Export all data and remove noncompatible field on selecting Import Compatible Option