Improve GL200 decoder (fix #830)
Support PT502 binary messages (fix #825)
Eliminated the need for hardcoded protocol strings in the src/org/traccar/protocol/*ProtocolDecoder.java files.
Made BaseProtocolDecoder members "final" as they should not change after construction.
Updated BaseProtocolDecoder constructor to take three parameters (DataManager, String, Properties);  Removed second constructor;