Aexpect improvements / bug fixes

* aexpect support parallel unittesting

* Allow server's BASE_DIR to be set by caller.
  (allows sequestration of unittest test data)
    
* Allow Spawn class to alter server's
  BASE_DIR (supports unittesting)

* aexpect should timeout instead of busy-wait

* add aexpect common cleanup function

* aexpect classes should know server PID also

* includes server process in aexpect liveliness

* Add aexpect unittests

* aexpect server should log debugging info

* aexpect shouldn't have empty string reader list