Malaurie's work on UI + CLI interface + AccelStepper interface

See merge request !17

Begining of the buttons' code, the button A  and B allows to go forward/backward slowly and fast depending on if the button is held, the button C allow to stop the syringe_pump movement at any time. I still have to add te reset when we hold button C.

The web method style is now divided in two methods, full_style and part_style to avoid changing style that are invisible on the graphical interface

Button throuput or duration work, their sliders too, and I created 2 attributes of web class to be able to refresh different information at different time.

that has been replaced by an attribute of web named exchange

Caging the clockwise_equals_push to clockwise_equals_forward and adapt fast/slow forward/backward bbutton for them to really work with this new feature

Add a getter to update the limit switch right when it et pressed/released and do not clutter the web_loop

-Add 2 attributes to syringefilled : throughput (boolean to kwow if we
work with vol/duration or vol/trhoughput) and update_remaining_volume (a boolean to know when we have to update the remaining volume
-Fix conversions methods of syringe_filled
-fix start_exchange method of syringe_filled
-add graphical interface for the two new attributes
-add a ne button to load syringe database