add label check to add link
add label check to save link
add label check to add/save song
adjust test
Merge branch 'master' of github.com:denkmal/denkmal.org into issue-89
set correct error with translation
Use german keys (then remove translation from 1.php)
check in save if the label is not from the own model
Merge pull request #89 from mariansollmann/issue-89

check in link "lable" already exist, DB error