implement deleting of message template when corresponding mosaico template is deleted 

Fix exception in the `testDelete` test.

Resolve #16 Regenerate auto generated civix files

Previously, inserting literal was handled if CIVICRM_MAIL_SMARTY was
set, which is irrelevant to non-CiviMail mailings.

Also, it previously only supported HTML5 style (no type attribute).

Now it wraps style in literal tags and wraps those in HTML comments, so
if smarty doesn't process it, it still works.

[#13] implement html filter

Fix for issue #6

adding smarty known issue to README.md

Few fixes, improvements

Clear Caches before running Job

Clear the caches before running the mosaico_msg_sync job in the upgrader.

This logic comes from `CRM_Mosaico_Utils::processDl()` circa v1.x.