Merge branch 'mailconverter-latest' into 'master'

standalone #1639 mailconverter custom actions

With this modification it's possible to add custom actions to mail converter just like custom workflow function! New action would be displayed along with default actions.

Follow this example:
```
require_once('modules/Settings/MailConverter/handlers/MailScannerEntityMethodManager.inc');
$emm = new MailScannerEntityMethodManager($adb);
$moduleName='HelpDesk';
$methodName='createticketcustom';
$functionName='createticketcustom_helpdesk';
$functionPath='modules/yourmodule/yourmoduleHandler.php';
$emm->removeEntityMethod($moduleName, $methodName);
$emm->addEntityMethod($moduleName, $methodName, $functionPath, $functionName);

See merge request !838