Refactoring of code shared by acq_irrad_interactive() and acq_fraction_interactive()

[aphalo]

The remaining functions need to be updated to include the features added recently to acq_irrad_interactive() if these features are useful.

[aphalo]

When implementing the new features in additional functions, we need to see how much code from acq_irrad_interactive() can be refactored into separate functions, both to make the code base smaller, but also to make easier coordinated updates of irradiance and fraction related functions.

[aphalo]

• Update acq_fraction_interactive() to incorporate all improvements made to acq_irrad_interactive().
• Refactor as much shared code as possible before their code diverges once again!

The functionality of the "irrad" and "fluence" acquisition functions is now all in acq_irrad_interactive() and the development of acq_fraction_interactive() has catched up and these two functions share a lot of code. As each function contains a lot of code, moving the shared code to separate utility functions seems like the best option. However, some of these functions would require many formal parameters, suggesting that it is best to start by collecting related sets of parameters into lists that can be more easily passed between functions and stored together as presets.