Enhance branding configuration (& refactor)

[poikilotherm]

Relates to #7649 and #7424

Currently, BrandingUtil does not do much more than handing back what you gave it. #3611 and #2710 where about options to override things.

So let's create new MPCONFIG variables:

1. dataverse.branding.installation.name, defaulting to the root Dataverse collection name
2. dataverse.branding.support.name, defaulting to root Dataverse collection name + contact.support bundle string as is now
3. dataverse.branding.support.mail, defaulting to dataverse.mail.system.from introduced for Move Java Mail configuration to application #7424

These can be either injected via CDI or retrieved programmatically via Config.getValue().

Easiest way to go IMHO: add a LookupConfigSource that has access to the necessary database services and might be used for other stuff down the road.