Add a config option to disable notifications for the user creating/updating a Call/Meeting

In this pull request we a config option to disable the notification for the current_user when creating or modifing a Call/Meetings. 

The user is also invited on the Meeting/Call so it would show correctly on the CalendarView. 

This setting only disables the email notiifcation to the current user. 

To enable this feature you must add 
```
$sugar_config['not_notify_current_user'] = true;
```
in config_override.php

Fixes #issue_48696: http://www.sugarcrm.com/support/bugs.html#issue_48696