Shipments, refactoring of HasState and strong params

 * IMPORTANT: tests for the new functionality are still missing!!
 * New type of state machine: shipment (for booth boxes and similar)
 * New roles to support the shipment workflow
 * Strong parameters instead of protected_attributes
 * Refactoring of HasState, moving more and more logic into the concern
 * State machines (Request, Reimbursement, Shipment) can only be edited by the
   requester and only in initial state. Added additional actions to support
   setting the approved amount and similar actions.
Seeds for roles :material and :shipper
Access control, corrections and tests for shipments and related changes
Comment ruby-debug in spec
Updated bootstrap-multiselect
Bootstrap-multiselect in filters
Added link to see/create reimbursement in the requests list
Avoiding the use of 'label' as column class
Missing reimbursement reminders
Reimbusement reminder sent only to requester
Version 1.1pre1
Changing the i18n for more intuitive names
Turn delivery_address into a separate PostalAddress model
Version 1.1pre2
RequestExpense renamed to Expense

 * The association with Request becomes polymorphic in order to allow future
   classes with reimbursement process.
 * See https://progress.opensuse.org/issues/2496#note-5
Revert "RequestExpense renamed to Expense"

This reverts commit 10c3070588464284f26afc5dd70cdedc763e9005.
Renaming models and creating a Request hierarchy

 * According to https://progress.opensuse.org/issues/2496
 * Now we have two abstract classes: Request and ReimbursableRequest
 * Request becomes TravelSponsorship < ReimbursableRequest
 * Shipment becomes Shipment < Request
 * RequestExpense and Reimbursement are now attached to ReimbursableRequest
   instead of Request
Add /requests GET routes for backwards compatibility
Implemented notify_to macro for more flexible reminders

 * Config option days_for_reminder is not used anymore.
 * Recipients and reminders are now set individually by state in the
   class definition of every state machine.
Transitions permissions moved to has_state

 * New macro allow_transition added
 * Methods like allow_xxx? can be defined for greater flexibility
 * Streamlined Ability