Improve document on Phase1

	Clarify the functionalities of Phase1 in README.mdown.
Add COSN Storage Class Skelton

	COSN Storage Class, CosnStorage, is defined in this file so that
	multiple cloud storage providers can be used in COSN. This receives
	another class which implements basic cloud io logic, and uses that
	cloud storage class to store and update files COSN uses such as
	location.xml, publicProfile.xml and content.xml.