*: numerous updates to match spec

Changes to schema:
- removing FilesetManifest
- update example manifest to match that in spec
- splitting out App into a dedicated type embedded in AppImageManifest

Changes to tools:
- update aci writer (no more filesets)
- update actool build (no more filesets)
- update actool validate (no more filesets)
- update ace validator to use new types
- update rocket stage0/stage1 to new schema
- update ace app manifests to new spec
- fix a bug in build_aci (double compressing aci)