add ProgressStatus model

Signed-off-by: Tomas Neme <lacrymology@gmail.com>
add default ID to make sure always the same object is returned

Signed-off-by: Tomas Neme <lacrymology@gmail.com>
current frame status-specific backbone.io backend

Signed-off-by: Tomas Neme <lacrymology@gmail.com>
shorter backend name

Signed-off-by: Tomas Neme <lacrymology@gmail.com>
Merge pull request #132 from inaes-tic/Lacrymology/frame-status

Send progress status to frontend.