SNOMED language and localisation support.
There are four ways to consider locale in SNOMED CT.
1. A crude language label (e.g. "en" in each description.
   This should generally not be used.
2. Requesting using one or more specific language reference sets.
   This provides the most control for clients but the burden of work
   falls on clients to decide which reference sets to use at each request.
3. Request by a dialect alias.
   This simply maps aliases to specific language reference sets.
4. Request by IETF BCP 47 locale.

Options 1-3 are defined by SNOMED.
Option 4 provides a wrapper so that standards-based locale priority strings
can be used effectively.

Arguably, there are two separate issues. For clients, they want to be able
to choose their locale and this should use IETF BCP 47. For any single
service installation, there will need to be a choice in how a specific
locale choice is met. 

Optimised hand-crafted serialization of SNOMED entities.

Store provides access to a key value store.