Add support for iterative builds and custom task names

[AndrewJRichardson]

Hi,

Not sure if you are still supporting this but I added some basic support for iterative builds as well as custom task names (useful for some distributed build systems which use custom CL tasks).

It adds Newtonsoft.Json as a dependency just for ease of reading and writing the file.

Tested on a large code base (AAA game and engine) and it worked as expected.

[0xabu]

Hi there! Thank you for the contribution and sorry for the delayed reply.

You guessed right -- I'm not using this any more, and really don't even have an environment in which to test it. Since your changes are non-trivial, it's probably better that you fork the project than that I take it in my repo. I'm happy to link to your fork.

[0xabu]

BTW you probably want to update the docs at some point :)