upgrade to version 4.2.0

[StCyr]

TODO:

• [x] fix the welcome screen

[StCyr]

Implemented on https://test.dmponline.be

[StCyr]

There are a lot of changes due to the migration to bootstrap 5.

Specifically, I had to merge changes on the following files manually. So, it is important to test the associated functionalities thoroughly to make sure I didn't break anything:

1. ./devise/mailer/invitation_instructions.html.erb
2. ./devise/registrations/edit.html.erb
3. ./devise/registrations/_personal_details.html.erb
4. ./layouts/_footer.html.erb
5. ./layouts/_navigation.html.erb
6. ./user_mailer/_email_signature.html.erb
7. ./static_pages/help.html.erb
8. ./static_pages/privacy.html.erb
9. ./static_pages/about_us.html.erb
10. ./paginable/plans/_privately_visible.html.erb
11. ./org_admin/shared/_theme_selector.html.erb
12. ./orgs/_profile_form.html.erb
13. ./orgs/admin_edit.html.erb
14. ./shared/_access_controls.html.erb
15. ./shared/export/_plan_txt.erb
16. ./shared/export/_plan_styling.erb
17. ./shared/export/_plan_coversheet.erb
18. ./shared/export/_plan.erb
19. ./shared/_sign_in_with_shibboleth.html.erb
20. ./home/index.html.erb
21. ./contributors/_form.html.erb
22. ./phases/_edit_plan_answers.html.erb
23. ./contact_us/contacts/new.html.erb
24. ./public_pages/template_index.html.erb
25. ./plans/new.html.erb
26. ./plans/_project_details.html.erb
27. ./plans/_share_form.html.erb
28. ./plans/_navigation.html.erb
29. ./plans/_download_form.html.erb