Update MAVLinkPayload.java

Need to type cast long and int on masks otherwise you'll get signed extension in java. I believe the byte order should also be swapped but I haven't had time to confirm for sure.
Update MAVLinkPayload.java

Added getLongReverse	

//getLong is broken when using uint64_t from APM's to pack bit commands
	//Created this to use on my custom message unpack so as to not break anything else with getLong downstream.
Update MAVLinkPayload.java
Merge pull request #396 from aussiemod/master

Update MAVLinkPayload.java