Locale-aware formatting for dates and numbers

[zone117x]

All locale-specific fields must currently be formatted as culture-invariant. This is primarily because all pages can be rendered on the server.

These fields include:

• Dates -- formatted as UTC
• Numbers -- formatted with a . decimal separator, i.e.123.456

One approach is to perform a locale-aware formatting pass on the client, for example in the ComponentDidMount hook.

Related to https://github.com/blockstack/blockstack-explorer/issues/205