Performance XML log format is in http://jakarta.apache.org/jmeter/usermanual/listeners.html
There are two different tags which delimit jmeter samples:
httpSample for http samples
sample for non http samples
There are also two different XML formats which we have to handle:
v2.0 = "label", "timeStamp", "time", "success"
v2.1 = "lb", "ts", "t", "s"
JUnit XML format is different : tag "testcase" with attributes : "name"
and "time".