Update CSSProperties.json

CSS Code Hints updated with properties and attributes from my Brackets-CSSCodeHints extension.
https://github.com/coliff/Brackets-CSSCodeHints

Properties and attributes added:
- background-size ("initial", "inherit")
- caption-side ("right, "left")
- clip-path ("auto, "inherit")
- image-rendering ("auto", "crisp-edges", "inherit", "pixelated")
- tab-size
- touch-action ("auto", "none", "pan-x", "pan-y")
- will-change

Pull request as requested by @jasonsanjose . Thanks - hope to see this in Brackets Core soon. :-)
`inherit` and `initial` are not valid values for `background-size` as per [specification](http://dev.w3.org/csswg/css-backgrounds/#background-size).