Expose Nuxeo resources via ContentProvider model

ContentProvider is a standard way of exporting content between application, this is useful for sending a Nuxeo Blob or Image to an external activity that will be in charge for displaying or editing it.

• content://nuxeo/documents : access to all documents
• content://nuxeo/documents/<UUID> : access to document with given UUID
  *
• content://nuxeo/<providername> : access to documents in the given provider
• content://nuxeo/<providername>/UUID : access to document with UUID in the given provider
• *
• content://nuxeo/icons/<subPath> : access to small Nuxeo icon of the given path
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• content://nuxeo/blobs/<UUID> : access to main blog of the doc with the given UUID
• content://nuxeo/blobs/<UUID>/<idx> : access to blog [idx] of the doc with the given UUID
• content://nuxeo/blobs/<UUID>/<subPath> : access to blog in the field <subpath> of the doc with the given UUID