Improve the LOG_DRIVER and LOG_COMPILER for the system tests

Improve the LOG_DRIVER and LOG_COMPILER for the system tests

There are several improvements over the default/previous behaviour of
the test log driver and log compiler:

 * The system-test-driver.sh was dropped (it was used incorrectly)
 * The run.sh script is now both log compiler and cli script to run
   individual tests
 * The custom-test-driver was added as extended version of the automake
   test-driver with capability to tee the test output to stdout when
   `--verbose yes` is passed to it (you can use LOG_DRIVER_FLAGS to
   add the option by default)
 * Makefile.am has been extended to honor V=1 for the system tests
   test-driver (e.g. V=1 adds `--verbose yes` to AM_LOG_DRIVER_FLAGS)