Define MySQL port by its own (rather than in the host with :port)

As the title says, this MR allows defining the MySQL server port in a new variable.

After having done the work I saw that it can simply be passed with the hostname, like `hostname:port`....
so I'm not going to be sad if this MR is getting closed asap. *rofl*

Leaving it here anyway.

See merge request !187

Ensure the internal PHP scripts work even if system-wide PHP settings are set

Another solution would be to reference the `php.ini` in `./server/lib` from all scripts...but maybe that's a bit of an overkill.

See: http://bugtracker.ispconfig.org/index.php?do=details&task_id=3293&project=3&string=php&type[0]=&sev[0]=&pri[0]=&due[0]=&reported[0]=&cat[0]=&status[0]=open&percent[0]=&opened=&dev=&closed=&duedatefrom=&duedateto=&changedfrom=&changedto=&openedfrom=&openedto=&closedfrom=&closedto=&pagenum=2

See merge request !188

ProxyPassMatch is only possible if running PHP-FPM over TCP

This fixes an error when `mod_proxy_fcgi` is installed/enabled but PHP-FPM is listening on a socket.

See merge request !189

ensure the internal PHP scripts work even if system-wide PHP settings are set that could affect how ISPConfig would work. See FS#3293

Conflicts:
	install/dist/lib/fedora.lib.php
	install/dist/lib/opensuse.lib.php
	install/lib/installer_base.lib.php
	install/sql/ispconfig3.sql
	install/tpl/config.inc.php.master
	interface/lib/classes/aps_crawler.inc.php
	interface/lib/classes/auth.inc.php
	interface/lib/classes/plugin_backuplist.inc.php
	interface/lib/config.inc.php
	interface/lib/plugins/mail_user_filter_plugin.inc.php
	interface/web/login/password_reset.php
	interface/web/sites/templates/web_backup_list.htm
	interface/web/sites/webdav_user_edit.php
	interface/web/themes/blue/ispconfig_version
	server/plugins-available/backup_plugin.inc.php
	server/plugins-available/shelluser_base_plugin.inc.php

Master

See merge request !186

This reverts commit 1357c3e3.

Prevent empty hostname during install

See merge request !184

'repeat password'-query if the default password is not used

See merge request !183