[FIX] fixed missing adaption PeptideIdentification::empty()

    last commit 8c2f86 missed apdation of method 'emtpy()'
    to new introduced attribute base_name_
Merge branch 'develop' into feature/track_peptide_identifcation_base_name
[FIX,TEST] adapted test for PeptideIdentifaction::empty
[NOP] adapted formatting
Merge pull request #752 from uweschmitt/feature/track_peptide_identifcation_base_name

[FIX] fixed missing adaption PeptideIdentification::empty()