Parse and format Java .properties files per the JDK spec. Handles =/:/whitespace separators, line continuations, \uXXXX unicode escapes, and comments. Convert to and from JSON, or ASCII-escape non-ASCII characters like native2ascii.
# or ! are comments (after optional leading whitespace).=, :, or whitespace run.\ is continued on the next line (leading whitespace stripped).\t, \n, \r, \f, \\, \=, \:, \uXXXX.\uXXXX if the ASCII option is enabled.