Move pointMult function to highlevelcrypto

Copy pointMult function from class_addressGenerator.py to highlevelcrypto.py
Move pointMult to highlevelcrypto

Remove pointMult from class_addressGenerator
Update pointMult calls to highlevelcrypto.pointMult
Move pointMult to highlevelcrypto

Update pointMult calls to highlevelcrypto.pointMult
Use pointMult instead of arithmetic.privtopub

pointMult is faster than the pure python arithmetic.privtopub

Additionally in makeCryptor the call to a.privtopub could have just simply be changed to call the local privToPub but then privkey would have been dehexified twice (once in makeCryptor, then again in privToPub) and privToPub would have hexified its result only for makeCryptor to immediately dehexify it. This sort of unnecessary hexifying/dehexifying seems to occur throughout PyBitmessage.
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
Refactor handling of packet headers

Refactored ackDataHasAVaildHeader:
 -shared.Header is used as necessary
 -avoided slicing wherever possible
 -remove trailing null characters when comparing command strings
 -don't calculate the checksum of a large payload
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
Refactor generation of packet headers
Refactor header generation

Modify generateFullAckMessage to use shared.CreatePacket
Fix syntax error
Fix name error
resolve merge conflict
Merge pull request #687 from Atheros1/bmng-dev-master

Bmng dev master