Escape any character in property names

[GoogleCodeExporter]

For Issue 7, the code looks explicitly for \\@  as an escaped element in the 
field name. This is a great feature that should be expanded to include other 
characters that need to be escaped, like dash ('-'). It is common to have 
dashes in field names:

{
  "first-name" : "Matt",
  "last-name" : "Bishop"
}

Original issue reported on code.google.com by m...@thebishops.org on 13 Dec 2011 at 9:17