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().
bin.includes = feature.xml,\
Carbide_Image.png,\
license.txt,\
feature.properties