major refactor to wrap retieval of macros all around ISymbianBuildContext, to avoid need to access internal apis. Added getTargetTypeMacro(String targettype), List<IDefine> getMetadataMacros(), List<IDefine> getBuildMacros().

name=name
nameDescription=unique name in this design -- basis for resource and C++ instance name 
className=class name
classDescription=C++ class name
design=Design
layout=Layout