Moving toggler widget from Wikibase to ValueView extension

Correlates to change I4a65397433815e8a9cc17f1367126d667f87a76b
in the Wikibase extension.

Change-Id: I0af51b2655e7a54e5f50a856c773ac0a38e29c63
Merge "Moving toggler widget from Wikibase to ValueView extension"