Release 6.20.1: deprecation of OXContextInterface.checkExists

[changerequest]

The RMI method OXContextInterface.checkExists as introduced with release 6.18.1 will be marked as deprecated. This method was only available to the RMI API (no SOAP/commandline implementation).

Please use the new method OXContextInterface.exists, which is introduced with 6.20.1 and is also available in the SOAP API and commandline interface.