Improve script output

* Fix postData parsing from har file

* Move createRequest commands to TestRunner class scope to prevent jython
  exceptions due to Java code length size: http://grinder.sourceforge.net/faq.html#faq-N1058A

* Simplify header output

  Instead of dumping the headers for every request, only *two* header
  descriptions will be used based upon the http request method used.

  The amount of headers being dumped to the global scope caused issues with
  the Java code length limitations.

* Add more exclusion urls