[REVIEW-REQUEST] RT-21709 Consider making available the CSS Styleable* classes as public API

[David Grieve]

Relative to http://javafx-jira.kenai.com/browse/RT-21709, I have posted a proposed CSS API to support the development of custom UI Controls. The proposal covers the API needed to make a JavaFX property styleable through CSS and the API for creating pseudo-class state. The proposal may be found athttps://wikis.oracle.com/display/OpenJDK/CSS+API+to+support+custom+UI+Controls. 
Please take a moment to review the document and provide feedback. 

Thank you.