Fix for \a or \v, because  Java does not recognize in strings

There is a problem with Bell Char (0x07) and Line tabulation char (0x0b) which Java does not recognize.
They are encoded as \a and \v for example in com.google.protobuf (http://code.google.com/p/protobuf-java-format/source/browse/branches/r47-antbuild/src/java/com/google/protobuf/JsonFormat.java) during serialization to JSON.

I added fix for above problem with test included.