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.
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.
Use all Person, not only Doctor for select in default biller and provider tenant fields.
Update CHANGELOG.
Link to booking templates.
Add CHANGELOG.
Update CHANGELOG.