Enhancement: Tooltips

We've used uikit to display tooltips before, now we added a own `v-oc-tooltip` directive and use this instead.
This improves accessibility and possibilities for later re-use.

https://github.com/owncloud/owncloud-design-system/pull/1263
https://github.com/owncloud/owncloud-design-system/pull/1271
https://github.com/owncloud/owncloud-design-system/pull/1272
