Db backend#1

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gorillainduction wants to merge 7 commits intomasterfrom

Commits on Nov 6, 2019

Add possibility to have a separate db backend to the merkle tree
Tobias Lindahl
committed

Commits on Nov 7, 2019

Extend testing to cover both old format and with a DB
Tobias Lindahl
committed
Add testing of using an imperative, stateful db backend (ets)
Tobias Lindahl
committed
Add documentation about db trees
Tobias Lindahl
committed

Commits on Nov 12, 2019

Add traversal of nodes in the merkle tree
Tobias Lindahl
committed
Handle compile warnings
Tobias Lindahl
committed
Improve edoc-ability of docs
Tobias Lindahl
committed