Removed 'debug' property from BuildType: will be added in a later story
Introduce a better DSL for specifying target architecture

- Removed Platform.Architecuture enumerated type
- Added notation parser that translates architecture string in Architecture
- ArchitectureInternal introduces some underlying structure used to determine architecture equivalence
Added "operatingSystem" property to Platform

- Models major operating system families only
- Notation parser used to convert string name into typed OS
- Not yet processed by tool chain implementations
Add support for building for Itanium architecture with VisualC++
Use internal OperatingSystem type for implementation of public type
Use the container API for creating default build type and platform
Inject parsers into DefaultPlatform