Create a unified interface for the tagpack DB

[soad003]

All clients currently access the tagpack db directly. This has many downsides a) it makes changes to the tagpack db harder since we don't have direct control over how the data is accessed b) leads to duplication of code for eg. standard access patterns to the db.

In the long run the graphsense tagpack db should become more standalone with a well defined (rest) interface for clients to consume.