[protocolbuffers\message] fix appendNNN method refcount problem
[protocolbuffers\message] use enum instead of magic number
[protocolbuffers\message] use same function for getter
[protocolbuffers\message] use same function for setter
[protocolbuffers\message] add append stub function
[protocolbuffers\message] use same function for has
[protocolbuffers\message] improve append method
[protocolbuffers\message] improve property name handling
[protocolbuffers\message] fix refcounting problem
[protocolbuffers\message] improve append method
[protocolbufffers\message] improve iterator validation