And found a small bug (privkeys were not deleted on zone deletion) which is now fixed
Testing successful. Doing last test then if everything goes well this will be the new merge request

* In addition to language specific custom welcome messages (when creating a new mail account) this patch will
allow to have a welcome message template for each domain.

* To add a domain specific welcome message, place a file at /usr/local/ispconfig/server/conf-custom/mail/
and name it according the domain, like welcome_email_example.com.txt

* i.e. /usr/local/ispconfig/server/conf-custom/mail/welcome_email_example.com.txt

will be used if a mailbox for example.com is created.

Dominik authored Dec 30, 2015 and Dominik committed Dec 30, 2015

After this, it is possible to use both:
 - sub.domain.tld
 - *.domain.tld
together with different folders by rewrite (with rewrite_type = L for sub.domain.tld)
Before it was not clearified which rule matches first, it always dependet on the creation-time of the subdomain

Conflicts:
	server/plugins-available/apache2_plugin.inc.php

- made placeholders visible for apache, too
- added event raise at formdef loading (on_before_formdef and on_after_formdef)
- added possibility to put plugin files into module/lib/plugin.d/ directory

- fixed letsencrypt domain list

- added cron for letsencrypt renewal

fixed error in mail_backup -> all mail-backups would have been deleted with old code because of * in filename

Conflicts:
	interface/lib/classes/remoting.inc.php
	interface/web/mail/templates/mail_user_backup_list.htm
	interface/web/sites/lib/lang/en_web_backup_list.lng
	interface/web/sites/lib/lang/es_web_backup_list.lng
	interface/web/sites/lib/lang/tr_web_backup_list.lng
	server/plugins-available/backup_plugin.inc.php