reporting during and after transfers

[xulman]

in GUI, there should be two checkboxes:

• do reporting at all
• if so, do verbose or tiny reports

Tiny reports: something like a progress bar (on a console), plus report transfer speeds
Verbose: replaces progress bar with what is currently there, plus report transfer speeds

In any case, even when no reporting at all, note in the log that the transfer is done.

[xulman]

• store in prefs store transfer speed of the currently finished transfer,
• use this prefs store value to estimate (and report) transfer time where appropriate (not in dialogs, only where more images are to be transfered)
• create a convenience API method that computes estimated transf. time given the prefs store value (implicitly given) and bytes to be transfered (explicit param)