Add support for old dashboards in content packs for new views

[kmerz]

Expected Behavior

When installing a Content Pack with a old dashboard the content pack facade should transform the old dashboard entity to a new view entity and install it as a new view dashboard.

Current Behavior

The content pack installation will fail.

Possible Solution

Add a new facade which will only transform old entities in new view entities and use the ViewFacade to install them.

Your Environment

• Graylog Version: 3.2 dev (573ce6cfa361dbbc7bf47a3903400b0fcc463cc6)

[danotorrey]

The content pack installation error due to dashboards can be reproduced with this content pack: content-pack.json.txt