[ADD] email_communication: new documentation regarding general emailing

Creation of a new submenu under Applications/General for the Email communication.
Moved advanced of dicuss to this new submenu + adding of content regarding
frequently asked question in support.

Redirection has been done on other files pointing to Discuss/Advanced to match
the new folder email_communication.

Modified content in:
- Email servers: split and move configuration part under email_domain
- Email domain: covering information about SPF DKIM and DMARC configurations by JQU
- Email templates: (how to use the functions) by GOR
- Email common: answering frequently asked questions + common issues by ALA

closes odoo/documentation#1550

X-original-commit: ce8a02d46a
Signed-off-by: Vergote Baptiste (bve) <bve@odoo.com>

content/applications/productivity/studio/concepts/understanding_automated_actions.rst

@@ -47,7 +47,7 @@ For every Trigger option, **conditions** can be applied, such as:
 - *Create New Record*: a new record with new values is created.
 - *Update a Record*: updates the record that triggered the action.
 - *Execute several actions*: defines an action that triggers other server actions.
-- *Send Email*: an automatic :doc:`email <../../discuss/advanced/email_template>` is sent.
+- *Send Email*: an automatic :doc:`email </applications/general/email_communication/email_template>` is sent.
 - *Add Followers*: followers are notified of changes in the task.
 - *Create Next Activity*: creates an activity such as: *Call*, *Email*, *Reminder*.
 - *Send SMS Text Message*: sends an :doc:`SMS </applications/marketing/sms_marketing/pricing/pricing_and_faq>`.