* refactors team views
* split views.py into users.py and teams.py in users app
* refactors method headers for _user_has_permission()
* adds method and class comments and documentation to base view classes
* refactors deduction views on interventions and eco accounts from function to class based
* introduces basic checks on shared access and permission on BaseView on dispatching --> checks shall be overwritten on inheriting classes
* refactors majority of user views into class based views
* introduces BaseModalFormView and BaseView for even more generic usage
* renames url identifier user:index into user:detail for more clarity
* adds sso_identifier as new User model attribute
* refactors minor code snippets on user-propagation data resolving
* adds updating of username based on propagation data
* adds sso_identifier on admin backend view
* fixes documentation and variable names on oauth token revocation
* introduces private key for propagation
* changes key usage in decryption of propagated user data from oauth_client_id to private propagation key
