Mainly move all pointer-map related helpers from app.rpc.commands.files
to the the app.features.fdata namespace and normalizes codestile around
feature handling on all affected code.
This commit also comes with several features related bugifxes on the
components-v2 migration code:
- properly migrate legacy feature names on apply components-v2 migration
- start using new fdata feature related functions
- prevent generation of a ephimeral pointer on each graphic migration
operation; on large files this caused a very noticiable overhead of
creating a big number of completly unused pointer maps
- do persistence after validation and not before
