[SIGMON-166] 'source consistency check' for analyze_multi_qh_voltage_current_with_ref

Context

• ticket: https://its.cern.ch/jira/browse/SIGMON-166

What was done

• check_dataframe_empty decorator accepts a list of strings with parameters' names to check
• consistency of sources is checked in analyze_multi_qh_voltage_current_with_ref

TODO

• nothing?

QA

• template link to sonar http://sonar.cern.ch/project/issues?branch=SIGMON-166_add_check_to_analyze_multi_qh&id=lhc-sm-api&resolved=false
• code was unit tested
• acceptance tests were written

Review objectives

• assessment of code functionality
• assessment of code quality
• identifying potential refactorings / logic common to other projects
• knowledge sharing