Resolve "relayhost change not reflected"

Closes #5805

See merge request ispconfig/ispconfig3!1237

Merge branch '5550-centos-7-installer-clamd-service-restart-message-in-error-when-not-installing-amavisd' into 'develop'

Resolve "CentOS 7 installer clamd service restart message in error when not installing amavisd"

Closes #5550

See merge request ispconfig/ispconfig3!1222

Use DANE if TLSA records are present

Closes #5786

See merge request ispconfig/ispconfig3!1235

backups:  # backups and default exclusions

Closes #3270 and #5787

See merge request ispconfig/ispconfig3!1233

Don't jump to top of page when checkbox is clicked

Closes #5791

See merge request ispconfig/ispconfig3!1234

Resolve "Discussion: Problems with removed old TLS and CIPHERS"

Closes #5770

See merge request ispconfig/ispconfig3!1232

return both email and cc when forward_in_lda=n

See merge request ispconfig/ispconfig3!1229

remove unneeded "certificate exists" message

Closes #5757

See merge request ispconfig/ispconfig3!1206

fixed server id and type limit on interface (from !1230)

See merge request ispconfig/ispconfig3!1231

Resolve "Directive snippets not saved and not applied"

Closes #5785

See merge request ispconfig/ispconfig3!1230

- removed master_directive_snippet code that was (in 2016) accidently backported from master but never used

- move all updates to onAfterUpdate
- remove server parts that are not needed

Custom PHP variables are not apply when configured in Directive Snippet

See merge request ispconfig/ispconfig3!1209

Merge branch '5784-missing-symlinks-to-etc-letsencrypt-live-on-certbot-during-install-update' into 'develop'

Resolve "Missing symlinks to /etc/letsencrypt/live on certbot during install/update"

Closes #5784

See merge request ispconfig/ispconfig3!1228

Resolve "subdomains DKIM Signing & rspamd"

Closes #5782

See merge request ispconfig/ispconfig3!1227

Resolve "Can't change Directives Snippes"

Closes #5780

See merge request ispconfig/ispconfig3!1226