Support "Include" in css-files

[FlorianKirmaier]

Currently cssfx doesn't support "include" inside of css files.
A lot of people are missing this feature.

[McFoggy]

looks difficult to support because here we would need to hook inside JavaFX internals resolution of the CSS.
If you have ideas, I am open to discuss them.

[FlorianKirmaier]

The JavaFX Internal resolution is probably relatively easy to mimic.

It's definitely very complicated. Reading the css-file, reading the include-statement, replacing them with the edited file, reloading the original file...
It would probably require various temporary files.
That would probably do the trick but it's very complicated.

Not planning to work on it at the moment.

#13 is probably more important and way easier, especially because it's very unexpected.