Feature: add option to switch on/off notification sound

[Guts]

Historically DicoGIS plays a sound (Tkinter.bell) when the files/database processing ends to warn the user that he has to open the application to save the workbook.

This PR:

• add an option to the GUI to enable/disable the notification sound
• add an option to the CLI to enable/disable the notification sound
• make this option settable with an environment variable
• use a custom sound from BigSoundBank

[codecov]

Codecov Report

Attention: Patch coverage is 8.33333% with 11 lines in your changes are missing coverage. Please review.

❗ No coverage uploaded for pull request base (master@fad5cf4). Click here to learn what that means.

Additional details and impacted files

@@            Coverage Diff            @@
##             master     #233   +/-   ##
=========================================
  Coverage          ?   20.40%           
=========================================
  Files             ?       38           
  Lines             ?     3083           
  Branches          ?      318           
=========================================
  Hits              ?      629           
  Misses            ?     2422           
  Partials          ?       32           

Flag	Coverage Δ
unittests	20.40% <8.33%> (?)

Flags with carried forward coverage won't be shown. Click here to find out more.

Files	Coverage Δ
dicogis/__about__.py	100.00% <100.00%> (ø)
dicogis/ui/main_windows.py	0.00% <0.00%> (ø)
dicogis/cli/cmd_list.py	0.00% <0.00%> (ø)
dicogis/ui/tab_settings.py	20.45% <0.00%> (ø)
dicogis/utils/notifier.py	0.00% <0.00%> (ø)