ocis web: configurable sw-license, help page links and logo

References:
https://github.com/owncloud/ocis/pull/12528 (feat: [OCISDEV-948] add configurable software license and help page links)
https://github.com/owncloud/ocis/pull/12529 (feat: [OCISDEV-950] make logo click-through URL configurable)

TBD where this will go (admin, dev or both)