Introduce proper KDoc parsing and Formatting

[strulovich]

The first version of Ktfmt uses the java-doc formatter from Google-Java-Format with very few forks to make it palatable. However, this will keep us stumbling onto issues. We need instead to figure a clean way to parse KDoc and output them instead.
@cgrushko pointed out that kotlinc can parse that, so this may be the first step to figuring out a good solution.

[strulovich]

We now parse KDoc using the built in lexers. There's definitely bugs and issues to resolve, but the results should be satisfactory for the vast majority of code. We will deal with specific issues from now on,