Fixed #4173 No SSL Tab for client if SSL available but also Let\'s Encrypt available template limit is active.

- added limit for letsencrypt and directive snippets selector to client limits
- hide ssl tab if letsencrypt is selected

- backported patches

- http://en.wikipedia.org/wiki/SPDY

- Directive snippets can now be made available to clients; clients can select an available directive snippet for a website - the appropriate snippet will then be written to the vhost configuration file. This is useful for example on nginx where clients have no access to the Options tab of a website.

(nginx still missing)

Conflicts:
	interface/web/sites/form/web_vhost_domain.tform.php

- Added fields to client, reseller and website to show when a record was added and by which user