Add PLATFORM_HAS_RADIO in Sky Platform

In order to use the er-server-example Radio resource it is required that the platform defines that it has a radio. This line might be required in other platforms.
Merge pull request #745 from PaulCorbalan/patch-1

Add PLATFORM_HAS_RADIO in Sky Platform
Merge remote-tracking branch 'upstream/master'

Conflicts:
	platform/sky/platform-conf.h
Remove Energy Harvester from sky conf.