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

Fixed query error impacting performances in inventory

This merge request is fixing and error in several queries impacting significantly performances if there are a big number of orders in the database.
Replaced:
vtiger_invoice_recurring_info.start_period = vtiger_salesorder.salesorderid
With:
vtiger_invoice_recurring_info.salesorderid = vtiger_salesorder.salesorderid

See merge request !842

mass_mail fix for #1559

fix for sending singularly mass emails from index view

See merge request !840

Price books popups fix

The pop up doesn't fill the values

See merge request !836

The pop up doesn't fill the values

#954 updates recaptcha

See merge request !832

Fixes #1630 Migration issue to update userlabel fixed

See merge request !831