[FIX] website_mail & calendar: demo data break the layout of mail design
[FIX] website_mail: can't be edit the mail template, javascript must be added into the asset
[FIX] website: remove multi consecutive dropzone
[FIX] snippets: use the new API to define dropzone
Merge pull request #2547 from odoo-dev/master-fix-mass-mailling-snippet-chm

[FIX] website_mail: can't edit mail templates