Various TrigValSteering test improvements

This is a collection of several small improvements for trigger ART test scripts based on TrigValSteering (ATR-20038).

Each change is a separate commit:

• Fix RegTest reference handling and TrigP1Test regex
• Add art createpoolfile pre-exec for grid tests
• Fix log zip step
• Skip ZeroCounts check for EmptyMenu tests
• Describe dry run option in README
• Add unit tests of ART test scripts

This merge request affects 5 packages:

• Trigger/TrigValidation/TrigAnalysisTest
• Trigger/TrigValidation/TrigP1Test
• Trigger/TrigValidation/TrigUpgradeTest
• Trigger/TrigValidation/TrigValTools
• Trigger/TrigValidation/TriggerTest

Adding @hartj ,@jpanduro as watchers

added Trigger master review-pending-level-1 labels

CI Result SUCCESS

	Athena	AthSimulation
externals
cmake
make
required tests
optional tests

Full details available at NICOS MR-26503-2019-09-11-22-35
Athena: number of compilation errors 0, warnings 1
AthSimulation: number of compilation errors 0, warnings 1
For experts only: Jenkins output [CI-MERGE-REQUEST-CC7 3189]

added review-approved label and removed review-pending-level-1 label

merged

mentioned in commit 92194a39

added sweep:ignore label