JCloud ProfitBricks provider implementation

Hi! This implements most of ProfitBrick's API. I look forward for your comments, suggestions, and revisions.
This property is used in the live tests, to pick the image to be used. jclouds by default tries to find an Ubuntu image, so unless it is explicitly needed to change that default here, just remove this property. Otherwise change it to a value that matches a real image in Profitbricks (if I'm not wrong this is the one used in DigitalOcean).