Introduce Encoder plugins Instead of abstract upload and thumb modules
Ported attachment routes. In v3 thumbnail depends on existing attachment
so route updated accordingly.
Some key points:
- Components and Plugins shouldn't extend Module directly
- Avatars should be fetched via GSActor ID, not by nickname as that isn't unique
- Avatar now is a separate Component
- Common file utilities are now to be placed in Core\GSFile, this will
handle storage and trigger validation
- Some bug fixes
