Improve identification of the temp directory and location of main log file

The temp dir is now in the form
                 <temp>/<user>/stressProof-<pid>

explicitely notified when starting the test.
The main log file (the one from the stressProof binary is now located under the
same test directory and named 'main.log'. E.g.

$ ./stressProof
******************************************************************
*  Starting  P R O O F - S T R E S S  suite                      *
******************************************************************
*  Temp dir for this run: /tmp/ganis/stressProof-31556
******************************************************************
*  Log file: /tmp/ganis/stressProof-31556/main.log
******************************************************************
...
Fix startup issue in master

  Introduced when adding support for SetParallel in dynamic setups in summer 2013.
  Never debugged because Proof in the master had other problems at the time.
Make names of being loaded PAR package SETUP macros unique per process

  Attempt to solve concurrency conflicts; does not hurt in general.