High level interface with easy to use in 3rd party stimulation scripts to embed qrcodes

[yarikoptic]

addition to

• Refactor python code into "reprostim" library to be shipped from pypi #116

so e.g. in the case of PsychoPy scripts, they could easily add smth like

import reprostim

## setup of their scripts
## right after getting trigger pulse:
reprostim.video_timestamp(experiment="1070_spacetop", id="the-beginning")  # or alike

...

and so on. This way we could then detect those QR codes in the videos, potentially associate with specific experiments etc, and thus avoid the need for absolute synchronization with MRI clock (we have an issue #TODO) ...