Proposal: Deprecation of non-receiver functions in packet package

Pull Request #92 moves to pointer receivers on the type Packet for interacting with the various fields of an mpeg TS packet. This creates duplicate functionality with functions that are already in place.
- Proposal: To create parity with the other packages we would like to move towards pointer receivers for all the functions that interact with packet. This means deprecating many of the current functions in packet.go

We would love input and guidance from the open source community on whether these are worthwhile changes. If this is decided to be a valuable change the old functions would be depreciated, and removed in a few months time.