Versioning - Add ability to override generating versioning information

[gjonespf]

Thinking of being able to do something like this:

BuildParameters.Tasks.GenerateVersioning.Task.Actions.Clear();
BuildParameters.Tasks.GenerateVersioning
	.Does(() => {
		Information("Add manual versioning here");
	});

This would enable you to build custom versioning schemes, use other tools as dropin replacements for GitVersion, or customise the GitVersion options completely.

[gep13]

Comment from @AdmiringWorm in duplicate issue...

Or maybe in a Setup instead, which can be conditionally disabled by the user if they want.
ie

#if !CUSTOM_VERSIONING
Setup<BuildVersion>((context) => {
  var version = new BuildVersion();

  // Do necessary logic for using versioning with gitversion

  return version;
});
#endif