[JT added installing netcat-openbsd in system.sh]

add a new autoconfiguration option PRIMARY_HOSTNAME=auto to simply grab the hostname from reverse DNS

drawn from https://github.com/Toilal/mailinabox/commit/5b23a06a7410e4530a56fd6200a6c46c3c6ea9b6.

move more of start.sh into questions.sh to keep start.sh cleaner and encapsulate all of the variable setting in a single script

Based on https://github.com/Toilal/mailinabox/commit/5b23a06a7410e4530a56fd6200a6c46c3c6ea9b6.

fix wrong redirect for automatic www subdomain redirects

$ curl -I https://www.site.co.il/static/images/1.png?a=b | grep Location
Location: https://site.co.il?a=b
but should be something like 
Location: https://site.co.il/static/images/1.png?a=b

This was broken by the ability to have multiple TXT records in 9f1d633a.

fix loop redirecting

server is redirecting the request for this address in a way that will never complete

* Set ssl_stapling_verify to off per https://sslmate.com/blog/post/ocsp_stapling_in_apache_and_nginx ('on' has no security benefits).
* Set resolver to 127.0.0.1, instead of Google Public DNS, because we might as well use our local nameserver anyway.
* Remove the commented line which per the link above would never be necessary anyway.

OCSP seems to work just fine after these changes.

the control panel auth hmac message should also include the user's password so that resetting a password in the database forces that user to log in to the control panel again; also use a sha256 hmac

when the undocumented custom web settings has a redirect or proxy at the root of a domain, use a minimal nginx config template (same as the new default www redirects)

* Split the nginx templates again so we have just the part needed to make a domain do a redirect separate from the rest.
* Add server blocks to the nginx config for these domains.
* List these domains in the SSL certificate install admin panel.
* Generate default 'www' records just for domains we provide default redirects for.

Fixes #321.

This doesn't change anything. Just preparation for the next commit.

if a user sets a custom A record on PRIMARY_HOSTNAME, which is ignored anyway, don't let that cause PRIMARY_HOSTNAME from being dropped from nginx.conf

Could be related to https://discourse.mailinabox.email/t/nginx-lost-admin-record-after-install-ssl-cert-problem/528.

bring the postgrey patches into this repository rather than maintaining them in a separate postgrey fork repository

* SMTP Submission (port 587) began offering the insecure SSLv3 protocol due to a misconfiguration in the previous version.
* Roundcube now allows persistent logins using Roundcube-Persistent-Login-Plugin.
* ownCloud is updated to version 8.0.3.
* SPF records for non-mail domains were tightened.
* The minimum greylisting delay has been reduced from 5 minutes to 3 minutes.
* Users and aliases weren't working if they were entered with any uppercase letters. Now only lowercase is allowed.
* After installing an SSL certificate from the control panel, the page wasn't being refreshed.
* Backups broke if the box's hostname was changed after installation.
* Dotfiles (i.e. .svn) stored in ownCloud Files were not accessible from ownCloud's mobile/desktop clients.
* Fix broken install on OVH VPS's.

fixes #414