Improve user error notification

[MiloradCvjetkovic]

Currently, SDS_ASSERT is used to detect if and SDS operation returned unexpected result.

Current SDS_ASSERT implementation here, just stores issue internally (in variable sdsError) but that will not be obvious to the user unless he understands and checks the sdsError.

I suggest we add printf to this SDS_ASSERT macro so that error information is printed to the STDIO and obvious for the user.

Since, that would print any error, the error SDS_PLAY_EVENT_ERROR_NO_DATA should be treated differently as that is a normal situation during playback, because sdsPlayRead is non-blocking it is expected to return SDS_PLAY_EVENT_ERROR_NO_DATA until all data is transferred via interface from the SDSIO-Server.

[ReinhardKeil]

Covered to an extend in #207