Persistent connection in the keystore

[aphelionz]

Overview

This PR implements the orbit-db-storage-adapter paradigm which has two main benefits:

1. Greater performance (see benchmarks below)
2. Easier Interop to redis, mongo, sqlite at the cache and keystore level via the storage adapter

Benchmarks

Before:

$ node benchmarks/benchmark-add.js
Starting IPFS daemon...
95 queries per second, 95 queries in 1 seconds (Oplog: 95)
87 queries per second, 182 queries in 2 seconds (Oplog: 182)
80 queries per second, 262 queries in 3 seconds (Oplog: 262)
88 queries per second, 350 queries in 4 seconds (Oplog: 350)
87 queries per second, 437 queries in 5 seconds (Oplog: 437)
85 queries per second, 522 queries in 6 seconds (Oplog: 522)
83 queries per second, 605 queries in 7 seconds (Oplog: 606)
88 queries per second, 693 queries in 8 seconds (Oplog: 693)
81 queries per second, 774 queries in 9 seconds (Oplog: 774)
--> Average of 86.1 q/s in the last 10 seconds

After:

$ node benchmarks/benchmark-add.js                             
Starting IPFS daemon...                                        
451 queries per second, 451 queries in 1 seconds (Oplog: 451)  
490 queries per second, 941 queries in 2 seconds (Oplog: 941)  
494 queries per second, 1435 queries in 3 seconds (Oplog: 1435)
513 queries per second, 1948 queries in 4 seconds (Oplog: 1948)
440 queries per second, 2388 queries in 5 seconds (Oplog: 2388)
415 queries per second, 2803 queries in 6 seconds (Oplog: 2803)
416 queries per second, 3219 queries in 7 seconds (Oplog: 3219)
375 queries per second, 3594 queries in 8 seconds (Oplog: 3594)
432 queries per second, 4026 queries in 9 seconds (Oplog: 4026)
--> Average of 445.3 q/s in the last 10 seconds  

Depends On

This PR depends on the following PRs:

• Fix/persistent store orbitdb-archive/orbit-db-cache#12
• Updates based on persistent keystore orbitdb-archive/orbit-db-identity-provider#29
• Persistent leveldb connection orbitdb-archive/orbit-db-keystore#30
• Default referenceCount from 64 to 32 orbitdb-archive/orbit-db-store#55
• use persistent store orbitdb-archive/localstorage-level-migration#4
• Persistent storage for append /caching performance orbitdb-archive/ipfs-log#251

TODO

• Replication still fails intermittently due to underlying js-ipfs bug (still function)
• Deal with failing v0 tests
• Deal with skipped tests
• Update docs

[aphelionz]

@shamb0t @haadcode All tests are passing except one replication test, and it's similar (though not the same) to the issues we're seeing in the v0 tests in ipfs-log. We're really close though.

I'm a bit spent today so I'm gonna take a rest but tomorrow I feel like we can together get this taken care of.

Note that I had to remove the usage of MemStore from test/replicate.test.js because it hadn't been updated to the base32 hashes. We can fix that up and restore it, or remove it completely.