Refactor tune params

[gustavdelius]

The spaghetti code has now been modularised and split over 4 files:

• tuneParams_controls.R has the functions for creating and processing the parameter inputs.
• tuneParams_tabs.R has the functions for creating the tabs and processing any controls on them.
• tuneParams_helpers.R has helper functions used by tuneParams().
• tuneParams.R has the tuneParams() function itself, now much more readable. This progresses issue #7