Update Copyright in README.
Fix stack overflow for Patient on newer Ruby/Rails versions.
Properly use print_payment_for setting from tenant.
Unify usage of settings on Tenant.
Use Person, not Doctor for Tiers#biller and #provider.
Add german translations for validation settings.
Common pagination style for treatments list.
Drop Tenant#doctor and use Tenant#person for #to_s.
Add de translation for Person model.
Show all persons as possible objects in the user relation form field.
Do not raise an exception when showing a session view for a session with no date set.
Update rails and support gems.
Update i18n_rails_helpers.
Add link to new treatment in patient view.
Fix invoices.print_payment_for setting usage in patient letter and reminder.
Merge remote-tracking branch 'origin/staging' into staging

Conflicts:
	app/prawn/patient_letter.rb
	app/prawn/reminder_letter.rb
Add pry console and debugger.
Add de translations for tenant view tabs.