CRM-21425: Add Permissions to Edit Inbound E-mails

CRM-21425: Add Permissions to Edit Inbound E-mails

The following permissions were added to CiviCRM core:

- CiviCRM: edit inbound email basic information
- CiviCRM: edit inbound email basic information and content

Having any of these permissions will alow  user to edit inbound E-mails, but
only the latter will allow users to also change the original email's content.

E-mails downloaded and stored as Inbound Email activities were saving their
details in two formats, as an ezComponents-parsed representation of
a text with alternatives. These alternatives were being stripped on the
Activity Form template, with the side effect of also stripping the textarea
where the wysiwyg editor would be built upon.

Fixed by stripping alternatives when preprocessing the quickform instead,
before the html for the textarea is generated.