Remove logo_change_allowed parameter

All marketplace admins should be able to edit the logo of their
marketplace.
Feedback emails go to admins or superadmins

Previously emails went either only to superadmins or to both admins &
superadmins. Now there’s no need to notify superadmins if the feedback
goes to admins.
Rebase to master
Merge branch 'logo-change-allowed' of https://github.com/sharetribe/sharetribe into logo-change-allowed
Removed defaults

Removed category_change_allowed, custom_fields_allowed,
terms_change_allowed and privacy_policy_change_allowed.
Feedback_to_admin defaults to true.
Remove mention of privacy_policy_change_allowed
Removed "editing_allowed", fixed remaining tests
Merge pull request #683 from sharetribe/logo-change-allowed

Remove unnecessary community defaults
Merge pull request #682 from sharetribe/feedback-to-admins

Feedback emails go to admins or superadmins
Draft of api spec for paypal payments
get payment info by transaction id
Use external merchant id, use symbols
Draft of accounts api spec
response bodies for token validation
Draft of billing agreements API
Billing agreement charge + reformat all
format Money types
Payments api skeleton
Add request payment implementation
Helpers for account and success response handling