Refactor generation of packet headers
Refactor generation of packet headers

Added global variable Header - a compiled Struct to pack/unpack headers so as to avoid repeatedly compiling the same format string
Add a new method CreatePacket to simply and efficiently construct a packet that is ready to be sent
Modify assembleVersionMessage to use CreatePacket
lightrabbit/PyBitmessage,torifier/PyBitmessage,krytarowski/PyBitmessage,JosephGoulden/PyBitmessageF2F,xeddmc/PyBitmessage,JosephGoulden/PyBitmessageF2F,torifier/PyBitmessage,timothyparez/PyBitmessage,xeddmc/PyBitmessage,lightrabbit/PyBitmessage,bmng-dev/PyBitmessage,hb9kns/PyBitmessage,mailchuck/PyBitmessage,hb9kns/PyBitmessage,Atheros1/PyBitmessage,rzr/PyBitmessage,torifier/PyBitmessage,gnu3ra/PyBitmessage,mailchuck/PyBitmessage,gnu3ra/PyBitmessage,Atheros1/PyBitmessage,mailchuck/PyBitmessage,metamarcdw/PyBitmessage-I2P,debguy0x/PyBitmessage,lightrabbit/PyBitmessage,debguy0x/PyBitmessage,kyucrane/PyBitmessage,Erkan-Yilmaz/PyBitmessage,timothyparez/PyBitmessage,hb9kns/PyBitmessage,lightrabbit/PyBitmessage,Atheros1/PyBitmessage,debguy0x/PyBitmessage,timothyparez/PyBitmessage,timothyparez/PyBitmessage,debguy0x/PyBitmessage,kyucrane/PyBitmessage,bmng-dev/PyBitmessage,Erkan-Yilmaz/PyBitmessage,Atheros1/PyBitmessage,metamarcdw/PyBitmessage-I2P,mailchuck/PyBitmessage,torifier/PyBitmessage,rzr/PyBitmessage,krytarowski/PyBitmessage,hb9kns/PyBitmessage,bmng-dev/PyBitmessage