Code from swarm that could be moved to ocean

[gavin-norman-sociomantic]

Some code utilities have built up in swarm that might be a good fit for ocean.

• ByteCountHistogram (Add BinaryHistogram ocean#441)
• TimeHistogram (Add statistics counter for generating a time histogram ocean#617)
• AcquiredResources (Add helpers for auto-relinquishing shared resources used by a context ocean#608)
• Code that deals with hashes

Other things that were considered, but seemed too specialised:

• TreeMap
• TreeQueue (Add ebtree TreeQueue data structure. ocean#618)
• StructPacker

[gavin-norman-sociomantic]

FieldSizeSum would be an obvious candidate for ocean.meta.

[gavin-norman-sociomantic]

TreeMap and TreeQueue could go in ocean.util.container.

[gavin-norman-sociomantic]

StructPacker is generic, but I'm not sure whether any other apps need to serialize structs in memory in this way.

[gavin-norman-sociomantic]

ByteCountHistogram (sociomantic-tsunami/ocean#441) and TimeHistogram could go in ocean.math.

[gavin-norman-sociomantic]

AcquiredResources is generic, but I'm not sure whether any other apps would benefit from it. Possibly other servers where the resources used to handle different requests vary significantly.

[gavin-norman-sociomantic]

The various bits of code that deal with hashes in swarm ought to be combined with similar code in ocean.