Report up/download progress

[mih]

osfclient only reports progress bars on download. We should disable those and report progress to git-annex (if possible), and have it do the reporting in a uniform fashion.

[mjboos]

Unfortunately the sessions library does not support upload streaming, but displaying upload progress might be possible in a hacky way - I can take a look at it tomorrow.

[adswa]

there are still no progress bars, contributing to confusion in e.g., #194