Use correct super-call.
Add inbox null-implementation to fix forwarding autocomplete.

Fixes #578.
Add specific icon and watermark-icons for subtasks.
Merge pull request #590 from 4teamwork/subtask_icon

Add specific icon and watermark-icon for subtasks
Merge pull request #580 from 4teamwork/deif-fix-forwarding-autocomplete

Fix an issue with autocompleting assignee/issuer while creating forwardings.
Moved DictStorageConfigurationContext to opengever.base.
Added option to disable download confirmation.
Catch up with latest changes on master, minor refactoring.
Add simple key-value store api.
Display portal message instead of 404 when attempting to download missing file.