Added Global Setting to Server config tab to
  - Enable & Disable the feature
  - Set the Proxy HTTP & HTTPS Ports

Added Per site level switch to enable and disable feature (Located in the Web Tab under the advanced section)

Added Apache2 and Nginx vhost updates to enable proxy_protocol on the listen lines

Added New database column to web_domain called "proxy_protocol" to enable site level config (Patch file Added upd_0089.sql)

Updated the Base Table SQL file to include "proxy_protocol" field

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

- fixed letsencrypt domain list

see:
- http://git.ispconfig.org/panders/ispconfig3/commit/f7ec00b2f8ba3efc5bdeacef9c813f8a826ae3be#note_453
- http://git.ispconfig.org/panders/ispconfig3/commit/f7ec00b2f8ba3efc5bdeacef9c813f8a826ae3be#note_452
- http://git.ispconfig.org/panders/ispconfig3/commit/f7ec00b2f8ba3efc5bdeacef9c813f8a826ae3be#note_450
- http://git.ispconfig.org/panders/ispconfig3/commit/f7ec00b2f8ba3efc5bdeacef9c813f8a826ae3be#note_449

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

- Added HHVM to "Default PHP Handler" field (server configuration).
- Fixed "Unable to load the server configuration from database." error when running server.sh.
- Fixed Javascript (accordions weren't working anymore, directive snippets and other placeholders couldn't be added anymore).

- nginx: added {DOCROOT} and {FASTCGIPASS} placeholders to directive snippets and nginx Directives fields.

Reverted SVN trunk back to revision 3938 to remove changes in default theme an a replacement of the ispconfig logo.

- Added backup size to web backups

If you change an auto subdomain of an alias/web-domain there has to be checked if a subdomain with www. or *. has been created already.

- New feature: you can now add directive snippets for Apache, nginx, and PHP under System > Directive Snippets. These snippets are then available on the Options tab of a web site where they can be easily added to the respective textarea by simply clicking the name of the directive snippet.