Parser functions are not discoverable

[jhugard]

The primary parser functions - which parse strings, streams, and files - are very hard to discover in the current namespaces:

Current names:

• Froto.Parser.Proto.parseFile
• Froto.Parser.Proto.parseStream
• Froto.Parser.Proto.parseString

Unfortunately, all the internal parse functions also live in Froto.Parser.Proto, making these primary functions very hard to discover.

Recommending that the primary parsing functions above get moved into a Parse module, and that the Proto parsers get moved into a Parse.Parsers module. Further, the parser parameter should be removed from those functions, so the user does not need to supply the pProto parser to these functions.

This simplifies client code down to the following:

open Froto.Parser

let statements = Parse.fromFile fileName

[jhugard]

Further, the Froto.Parser.Model module should probably get renamed to Froto.Parser.ClassModel, to indicate it is not the only means of representing a parsed protobuf file. In fact, the primary means of parsing should probably be via a Froto.Parser.Ast.PStatement list, as returned by Parse.fromFile.

[jhugard]

Note: the reason for these changes is that I went to use the NuGet package in a new project, and couldn't myself figure out how to parse a file without looking at the source code!