Define prepareData Function Interface between DDM module and Data Preparation

The Local DDM service will receive an external API invocation to prepare data to be accessible to a particular user area. After checking permissions, the Local DM service should invoke a simple interface to prepare the data like:

prepareData(String[] dataUID, String user)

or similar that could be implemented in different ways (e.g. simple creating a read-only link from the repository data to the persistent volume, add into user VOSpace or others possible future implementations) depending on the node infrastructure

This feature will:

• Define the API signature of this method
• Integrate into the Local DM service one particular implementation
• Prepare the Local DM service to accept other implementations (e.g. by using a Factory pattern)