* migrates to hive.go database package

* review fixes

* alias types and vars from hive.go's db package

* Move database to tempdir to prevent sideeffects in tests

* fix import

Co-authored-by: Wolfgang Welz <welzwo@gmail.com>

* refactors errors

* fmt packages/model/error.go

Signed-off-by: Luca Moser <moser.luca@gmail.com>

- lru cache
- soldifier for tangle
- ...