TVB-2659: Make "Next" buttons accessible by keyboard

Created by: VinczeRobert

So far I have made possible to run a simulation with default parameters by setting initial focus on the next buttons or on the launch/launch_pse in their respective fragments. When the focus is not on any active element (in that case the focus is by default on the body element) at the press of any arrow key, the focus will be restored to the next or launch buttons. Also, using left and right arrows it is possible to navigate through the buttons.

My first problem was that all the next buttons in every fragment have the same id, so I renamed them to "next/burst/{current_fragment_name}".

I don't like that I have a little hardcoded things there, so I'll try to find a better solution to get the initial fragment or to get only the fragment url out of the one having "localhost....". Besides these, should the select fields also be accessible by keyboards? Maybe we could use left-right only on the buttons and up-down on the data fields?