split config classes into separate files, add missing @Directive tags

[pabl0rg]

You may wish to do this yourself as this commit may skew statistics on the repo. These changes improve the index that can be auto-generated with https://github.com/pabl0rg/kobalt-dsl-documenter

[cbeust]

Yeah there's a lot going on in this PR, files moved around, spaces removed, etc... I'd rather have smaller ones.

Also, I'd rather keep the config in the same file as the directive (e.g. BuildScriptConfig and BuildScript, will that be a problem for your tool?

[pabl0rg]

Yeah those splits are necessary in order to reflect on the config classes (kotlin reflection does not support facade classes yet).