Make it possible to show less log entries again - fix owncloud/core#1593

 * show "less" button only if there are more than 3 entries
 * only "remove" logs till last 3 entries
remove animation
add copyright note
apply code review hints
convert js call to css rule
fix typo and remove animation
Merge pull request #2597 from kabum/lesslog

Make it possible to show less log entries again