Exec ConsoleToMSBuild=true doesn't preserve colors

@rainersigwald I've spent some time pondering some deep, Confucious stuff lately regarding my build toolchain, and started asking:

"How can I run a .NET Core CLI Tool in an MSBuild Exec Task AND preserve the color output?"

Oh, boy.

Along the way, I found that [MSBuild output itself can emit ANSI Escape Codes to processes like Travis CI](https://github.com/Microsoft/msbuild/issues/1792)... so it got me wondering, why can't MSBuild parse ANSI Escape Codes rather than generate them? Searching StackOverflow, I don't see any good answers. People seem to think fundamentally there is no way to capture color, it's [drastically impractical](https://stackoverflow.com/a/17493515/1040437), because color is a property of the console, not the standard output and error streams. I say, let there be color. [Pastel](https://github.com/silkfire/Pastel), maybe.

Here is a sample repro of the issue:

# build.targets
```xml

```

# Expected Output

"hi" in red.

# Actual Output

"hi" in console default foreground color and default background color

# Deep Thoughts

“I for one believe that if you give people a thorough understanding of what confronts them and the basic causes that produce it, they’ll create their own program, and when the people create a program, you get action.” — Malcolm X