Merge pull request #220 from dlu-gs/update-develop

Update develop - run composer update!
Removed unneeded fieldset tags from html output
Merge pull request #221 from dlu-gs/feature/twb

Removed unneeded fieldset tags from html output
Max number of items in Explorer Tree is configurable
Merge pull request #222 from dlu-gs/feature/tree-size-config

Max number of items in Explorer Tree is configurable
Merge remote-tracking branch 'v2/feature/backend' into update-develop