SOLID POD: create required folder structure when initialising POD

[cdawei]

Update solidpod so that the SolidLogin allows user to specify additional folders and files to be created when initialising a POD. For example, riodash uses the following folder structures to store device/session/treatment/participant info:

• data/device-configuration/
• data/session-configuration/
• data/participants/
• data/treatments/
• etc.
  Perhaps creating these directories when the user logs in riodash for the first time, ideally together within the POD initialisation process.