Properly escape GeoJSON

[oschrenk]

Right now GeoJSON isn't properly escaped.

1. It does escape double quote with two slashes. This only makes sense if the GeoJSON code is inlined in JavaScript, as two escaping mechanisms are needed.
2. It does not escape all characters required by RFC 4627

I suggest using either json-simple's JSONValue#escape method [1] (Apache license) or to adapt gson's sring method [2] (Apache license)

[1] ​https://code.google.com/p/json-simple/source/browse/trunk/src/main/java/org/json/simple/JSONValue.java
[2] ​https://code.google.com/searchframe#1W0hTXRl0vg/trunk/gson/src/main/java/com/google/gson/stream/JsonWriter.java&l=532

I was using JOSM to export a GeoJSON layer for Polymaps which choked on double quotes being escaped with two slashes.

[skyper]

escaped numbering.