Refactor packet header extraction and generation
Refactor packet header extraction and generation

Demote payloadLength from class instance variable to processData local variable as no other function was using it
Improve processData:
 -Utilise shared.Header
 -Use a memoryview to reduce memory overhead
 -Clean up variables before a recursive call
 -Strip null bytes from command
Refactor sendData
Various functions:
 -Use shared.CreatePacket to generate packets
Fix typo in _checkIPv4Address
JosephGoulden/PyBitmessageF2F,torifier/PyBitmessage,Atheros1/PyBitmessage,bmng-dev/PyBitmessage,mailchuck/PyBitmessage,rzr/PyBitmessage,torifier/PyBitmessage,bmng-dev/PyBitmessage,mailchuck/PyBitmessage,kyucrane/PyBitmessage,timothyparez/PyBitmessage,timothyparez/PyBitmessage,xeddmc/PyBitmessage,hb9kns/PyBitmessage,Atheros1/PyBitmessage,rzr/PyBitmessage,timothyparez/PyBitmessage,mailchuck/PyBitmessage,Erkan-Yilmaz/PyBitmessage,mailchuck/PyBitmessage,metamarcdw/PyBitmessage-I2P,hb9kns/PyBitmessage,debguy0x/PyBitmessage,bmng-dev/PyBitmessage,gnu3ra/PyBitmessage,Erkan-Yilmaz/PyBitmessage,lightrabbit/PyBitmessage,debguy0x/PyBitmessage,krytarowski/PyBitmessage,Atheros1/PyBitmessage,gnu3ra/PyBitmessage,lightrabbit/PyBitmessage,metamarcdw/PyBitmessage-I2P,lightrabbit/PyBitmessage,torifier/PyBitmessage,JosephGoulden/PyBitmessageF2F,lightrabbit/PyBitmessage,hb9kns/PyBitmessage,krytarowski/PyBitmessage,debguy0x/PyBitmessage,timothyparez/PyBitmessage,hb9kns/PyBitmessage,debguy0x/PyBitmessage,Atheros1/PyBitmessage,xeddmc/PyBitmessage,kyucrane/PyBitmessage,torifier/PyBitmessage