Make parsing in zerberus more robust

Currently we just scan for equal signs in the sfz files to structure the opcodes and their values - the only known opcode that might contain whitespaces is the sample opcode. All others should not contain white space - so split the data at the white space and use the first data field!

There is a formatting error in "SalamanderGrandPianoV3Retuned.sfz" from line 448 to 464 where the tune parameter is missing the equal sign. Currently pitch_keycenter gets a bad value (0) because of this.