Implemented Packet Header Processing
Implemented date/time field
WIP TDDS
Implemented composite field
WIP Implemented message type constants; need a MsgType field
Implemented lookup field
Added MsgType field to header
WIP: Implemented short form trade basic fields
WIP:  Implemented Trade Cancel/Error & Trade Correction messages
Fixed unit tests
WIP: test attributes
Implemented lookup field attribute
AlphaLookup field no longer needed with lookup field attribute
Fixed-up constants
Fixed msg type bug
Implemented TddsVariableText Field
Implemented General Admin Message
Implemented closing price summary mesasge
Implemented header-only control messages
Implemented Packet Header Processing