Mid Sensitivity Calculator Front-End refactor

Sensitivity calculator front-end uses Bootstrap and JavaScript. Currently to switch between the user and 'expert/debug' modes, the calculator needs to be run as two systems each serving almost identical HTML pages. These pages should be combined into one page where some inputs are shown/hidden based on the mode. It should also be possible to switch between the modes using the calculator UI. This also requires making design decisions on how the mode is displayed to the user so that it is clear which mode was used to produce the calculations.
Additionally the interactive input validation should be refactored to be more efficient and to use a library similar to Astropy for consistent astronomy units.