Remove outdated comment and related code

ApplicationPolicy has its own definition of #is_owned_by? and is this
one the available to all other subclasses.
Revert "Remove outdated comment and related code"

This reverts commit 2aba0d62b480657bfbf2571f23b2c309d3e20566.
Limit view of pages for non beta users
Include permission to partially view projects
Prevent links to discover_path to be opened for non authorized users
Make links to project_path compatible with permissions module
Use different modals for permissions when signed or not signed in
Scope search of email input in feature spec

Since a modal to sign up is always rendered in the page, Capybara will
find more than one email input in the entire html.
Send tracked events of permission denied to mixpanel
Allow waitlisted users to partially view projects
Protect issuance tabs and invest button from non beta users
Camel case in methods
Define front-end permissions for remaining project tabs
Merge pull request #767 from neighborly/im-users-accesses

Forbid access to some features for non beta users