- sending of SUBSCRIPTION and awaiting of NOTIFICATION have to be optional and PX_SIP_SUBSCRIPTION and PX_SIP_NOTIFICATION are used to trigger this procedure
- f_setHeaders_deREGISTER: empty vc_authorization header is set for correct REGISTER message, vc_branch have to be rand calculated again
- f_removeRegistration: vc_via is replaced with vc_via_REG to use correct global variable
- f_calculateCredentials* functions: upper/lower case problem within algorithm parameter value is handled due to received values from response 

- new TODOs: temp solution for 2nd option of deREGISTRATION which have to be replaced with commented 1st solution which is more general(see f_setHeaders_deREGISTER and f_removeRegistration functions) Solution done to have progress with validation.