StressGraph creates invalid JSON in cases when control characters are placed on the command-line

Several cases in tools/stress/src/org/apache/cassandra/stress/StressGraph.java use JSONObject.put (inherited from Map) without escaping the input. I encountered this when using -graph on windows and using a windows file path (such as C:\path). In this instance the backslash was un-escaped and resulted in invalid JSON placed in the output html/javascript, which caused the page not to render. There are other cases in this file when input is not escaped as well.

All values should be escaped (using JSONObject.escape(), for example) before being put into the Map.

ref: https://git-wip-us.apache.org/repos/asf?p=cassandra.git;a=blob;f=tools/stress/src/org/apache/cassandra/stress/StressGraph.java;h=ebaa0aecdb2db68485960013d4b6124c57fe1ac4;hb=HEAD lines 205, 210, 211, 213, 215, 216, 217, 252, 253