TauEfficiencyCorrectionsTool: run without PRW tool and remove obsolete ifdef

Add support for reading the RandomRunNumber decoration directly without needing the PRW tool.

• adds AutoTriggerYear property (false by default for backwards compatibility)
• run number is only read once per event
• README was updated as this yields much simpler configuration than using the PRW tool directly

Also remove obsolete TAUANALYSISTOOLS_PRWTOOL_AVAILABLE. For newer code it was not used at all and we should have PRW tool available in all analysis releases.

@dkirchme, @martindl, it would be nice if you can sign this off