Consider switching to a consistent levelup key type

[mhhf]

Currently different key types are used:

• number for accessing block numbers
• strings for meta-information such as 'meta', 'detail:' + ,
• buffers in merkle-patricia-tree

I've noticed weird behavior while working with on the persistency feature for ethereumjs-testrpc with leveldown - the persistent storage adapter for levelup: levelup uses red-black-trees to store data with a custom comparison function, if now different key types are used (I could observe this with Buffer and non Buffer keys) data is saved to a different location from where it is looked up for which results in saving data to a key and don't be able to get it again, leading to errors like this: trufflesuite/ganache-cli-archive#81 .
This is (temporary?) resolved by switching to a consistent key type (I refactored ethereumjs-blockchain to work with Buffer keys only).

Should I create a PR for this?

[wanderer]

@mhhf yeah pr would be great!

[vpulim]

This issue has been fixed in #52 by converting all key encodings to type 'binary'. We should close this.