aggregator2: allow the user to specify the MIME type of the response.
aggregator2: add dictionaries with translations based on the aggregator module.
aggregator2: clarify documentation about signing the aggregate.
aggregator2: add an index page that lists the available aggregates and links to them.
aggregator2: bugfix.
aggregator2: add filtering (by sets, as in the aggregator module) and entity exclusion (by entity ID). Both options can be set by request and as a default by configuration (per aggregate, not source). Both options accept multiple values (exclude several entity IDs, filter by several criteria). Results are cached according to the filtering and exclusion parameters.
aggregator2: fix package name.