Fixed Code analyzer warnings in Constants class.
Fixed unit test for SerializableExtensions class.
Updated Unity NuGet component.
Implemented USState value type and USStateType enumeration. Covered USState by unit tests.
Fixed code analyzer warnings in USState and USStateTest classes.
Renamed USStateType enumeration to EnumStateTypes. Flag enum names should be plural.
Added IsState, IsUnincorporatedTerritory, and IsMilitaryCode properties to USState value type.
Implemented extensions for USState class and appropriate unit tests.