Optimize number of API calls in ConsoleRenderTarget

[Athari]

Calling Console.Write for every line seems to be unoptimal compared to writing one big block of text. Probably caused by too much interop. See https://github.com/Athari/CsConsoleFormat/issues/21#issuecomment-378329169.

Optimize number of API calls in ConsoleRenderTarget for specific cases, like lack of color formating in the document or disabled formatting like discussed in #22.

Optimizations from #11 should make that unnecessary for modern platforms, but generic fallback console writing should be fast too.