Fix misnomer of NBFoundationAdditions

We're adding to Foundation, not NBFoundation.
Fix minor whitespace
Fix minor misnaming of credential class
Fix minor code style inconsistencies
Fix minor code style inconsistency
Cleanup minor client project file debris
Cleanup client properties implementation

Also add baseURL to initializer.

Cleanups:

- Factor out nationHost; baseURL is guaranteed.
- Stop checking launch args for baseURL format to
  get a custom baseURL.
- Remove unused and half-baked invalidation on
  nationName change.
Make custom client accessors KVO compliant

Leveraging the default setters instead of directly
setting on instance vars prevents obviates add
willChangeValueForKey: and didChangeValueForKey:
Merge pull request #7 from 3dna/peng/cleanup-1

Cleanup #1 (minor, unreviewed)