Switched to generalized input function

Using either apbase.multiple_choice or adapted input if either on OS X
or Linux. Only tested on Linux for the moment.
Nicer output in the exposure time setting function.

Fixes #4
Fixes #5
Also inputting Scintillator and Lens

- Changes to ask for Scintillator and Lens, fixes #2 and fixes #3
- Prettier output before the experiment starts

This works on *Linux*, testing on OS X to be confirmed before merging
into `master` branch.
Merge branch 'ivanify'