gui acqmng: add test case on cancel
gui acqmng: add basic thumbnail support
gui util: move, rename, and fix seconds2human

it's very similar to readable_str, so put it next to it.

support negative time, and microseconds.

add test cases
gui acquisition: connect to acquisition manager

connect close/cancel and acquire buttons to the acquisition manager

to get the streamTree required, a lot of changes were also needed at the interface level.
it should help also in showing the view.
gui: small fixes to get the acquisition working