TrigP1Test: HelloWorld test (ATR-19205)

@rbielski , @fwinkl

here is now a very basic implementation of the athenaHLT tests. Tests are submitted in exec_art_trigp1test.sh. Once athenaHLT has run, there are steps for merging outputs, post tests and a print out of the summary.

The current enabled tests are:

• Trigger/TrigValidation/TrigP1Test/test/test_HelloWorldHLT_OHMonitoring_build.sh

• Trigger/TrigValidation/TrigP1Test/test/test_HelloWorldHLT_build.sh

• Trigger/TrigValidation/TrigP1Test/test/test_HelloWorldHLT_forkAndMT_build.sh

• Trigger/TrigValidation/TrigP1Test/test/test_HelloWorldHLT_fork_build.sh

• Trigger/TrigValidation/TrigP1Test/test/test_HelloWorldHLT_run_stop_run_build.sh

I'll have to add the check for the child exit codes, skip post tests if not needed, fix merging of root files with option -M, fix rootcomp and other things