Bump major version for python package

[sindrehan]

The major versions for the blueye.protocol python package will now be:

• 1.5: Old tcp/udp based, with the blueye.protocol name
• 2.0: Same protocol as 1.5, but renamed to blueye.legacyprotocol
• 3.0: New protobuf-based protocol, published to blueye.protocol package