Use Haskell conventional haskell style for protobuf field names and protobuf enum values

[bitc]

message SongServerRequest {
  required string song_name = 1;
}

enum Foo {
  FIRST_VALUE = 1;
  SECOND_VALUE = 2;
}

In the generated Haskell, the record name for the field song_name should be songName, and the generated constructors for the Foo enum should be FirstValue and SecondValue.

This is to be consistent with the conventional style that is used in Haskell.

Note that a similar conversion is done in the official Java protocol buffers library. See https://developers.google.com/protocol-buffers/docs/style

[k-bx]

I like the proposal, looks good. One thing to note is that when implementing this, person needs to provide a flag --no-camelcase to hprotoc that would keep old behavior for people who have large code-bases and no motivation for the change