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 = META-INF/,\
               os/,\
               tcfPlugin.jar
jars.compiler.order = tcfPlugin.jar
source.tcfPlugin.jar = src/
output.tcfPlugin.jar = bin/