Implement the special Java character properties

[natecook1000]

These character properties are described in the regex syntax proposal but are not implemented:

... javaLowerCase, javaUpperCase, javaWhitespace, javaMirrored.

[hamishknight]

So it turns out that while those are the properties listed in Java's docs, there are actually quite a few more of them, as they correspond directly to various is accessors on java.lang.Character. I have put up a PR to parse them: #440.