Enhancement: Update extensions

We've updated various extensions to a tagged release:
- ocis-phoenix v0.4.0 (phoenix v0.7.0)
- ocis-pkg v2.2.0
- ocis-proxy v0.3.1
- ocis-reva v0.1.1
- ocis-thumbnails v0.1.0
- ocis-webdav v0.1.0

https://github.com/owncloud/ocis/pull/180