Use wait icon after selecting parameter file

[samnemo]

Should use the wait icon after selecting a parameter file in case the simulation was run and there is a lot of data to load (which could incur a noticeable delay).

[blakecaldwell]

I've added printing messages to the console when spectrograms are being computed/plotted. This is the most computationally expensive part of the GUI (besides running the sim). The GUI will still pause, but now that we don't have a docker install, the assumption is that the user can see messages on the terminal window. For example:

Extracting spectrogram from dipole
Extracting spectrogram from dipole
Extracting spectrogram from dipole
Extracted 3 spectrograms for ERPYes3Trials_173ms_opt
Plotting Spectrograms

If someone wants to take this up further, a progress bar popup would the most user-friendly solution. Would go here: https://github.com/jonescompneurolab/hnn/blob/b2803ffc21a2edaf53cee6167d4d83d103f92e44/hnn/qt_spec.py#L228-L229