* mail_channel, mass_mailing, twitter, event
- t-install attribute holds the technical name of the module that
needs to be install to use a particular snippet.
- Disable the drag & drop feature for these dummy snippets.
- Move some images to website module.
- Installed snippets display at the top of the list.
- Hide not-installed module snippets if user don't have rights to install module.
Commit 9676ceec02 removed/replaced image files in mass_mailing
module but two of them were still used by website_mass_mailing.
This commits adds these two images in website_mass_mailing module and
use a more standard convention to define associated snippets and
link them in the snippet panel. Also lint JS files.
Kishan Gajjar