* appcodechecker accepts boolean.
* using different ports in trusted domains

Partially fixes #330

Users often ask in IRC or the forum how to add another domain. 
Hopefully they will be able to find it out on their own if we have an example with two domains.

It isn't uncommon that admins create a backup file of the config (i.e. `config.php.bak`) before performing any changes. This would allow everybody to read the backup of the configuration file which contain several secret and critical values.

I don't believe this is worth a backport or getting added to the installer. It's just a nice to have. People that create public readable backups of their configuration are the one to blame, not us :-)

Whenever the reverse proxy is using "/" as the webroot, it is now
possible to set that value in "overwritewebroot"

When using an external cache folder, it is automatically mounted in
FileSystem::initFileSystem so that any app can use it transparently
by creating a view on the "/$user/cache" directory.

Fixes #2012

This can be confusing and/or annoying

When session_keepalive is true (default) the heartbeat will be send as
often as the half of the session timeout value.

do not share users data with config files

Signed-off-by: Tigran Mkrtchyan <tigran.mkrtchyan@desy.de>

/* Enable maintenance mode to disable ownCloud
   If you want to prevent users to login to ownCloud before you start doing some maintenance work, 
   you need to set the value of the maintenance parameter to true. 
   Please keep in mind that users who are already logged-in are kicked out of ownCloud instantly.
*/

add options to disable the check for a working .htaccess file in data and for a working WebDAV server. This are advanced settings that are needed in special situations where our check fail and the user runs into an http timeout.

This should help make OpenSSL configuration on Windows servers easier by allowing the openssl.cnf file to be set directly in the ownCloud config, rather than in SetEnv commands that don't exist and are hard to replicate in IIS.

Remove gravatar and no-avatar functionality, prepare for default avatars even more and reword some stuff