Script Generator: Improve user interface

As a user of the script generator I would like the user interface to feel intuitive and uncluttered. Currently buttons have been added to the user interface for every new feature without much thought as to the holistic view of the generator. We should tidy this up using tools such as:
* Icons rather than large buttons
* Right click menus

## Acceptance Criteria
* The Script Generator is less cluttered
* All functionality is still present and it is intuitive on how to access it - if possible ask a scientist to test it
* There is documentation on how to use the view (e.g. update https://github.com/ISISComputingGroup/ibex_user_manual/wiki/Using-the-Script-Generator)
* If appropriate right click menu for some options

## Notes

- Thought should be given to future iteration which will allow the user to have multiple tables for different sorts of actions, within one. Positions and sort of user buttons should still work.
- Also remember that this is a screen in IBEX GUI as well as part of the stand alone app.
- Use excel as a guide most people can use it but also remember that this application is different because excel has infinite cells in all directions and we do not.