set song to null when stop
add deleteEventtextCaches()
delete cache if link is add/save/delete
Revert "add deleteEventtextCaches()"

This reverts commit e73cb057a77a2b819be6987cfd3fdb4d40c0a641.
Revert "delete cache if link is add/save/delete"

This reverts commit 334c4ba072ee5333563bf6e5c44804cee92a66a1.
adjust docu to be null
Merge pull request #82 from mariansollmann/issue-82

Play button goes to playing mode