Successor Project task and view

[tinne]

It shall be possible to create a project as a successor to the selected project.

There shall be special task view for the creation of the successor. All current requirements are based on the assumption, that the relationship between a project and its successor are 1:1, where both the successor and the predecessor of a project are optional.

The project title of the successor project defaults to the current project title and must be changed, as project titles must be unique.

The beginning of the successor project shall default to the current project date (exclusive) and the default length of the successor project shall be a calendar year. The successor project period may be changed at will without verification (one time initialization only).

The users of the current project shall be proposed as users of the successor project. Every user except for the one creating the successor project may be removed from the list upon in the creation view. Additional users must be added later.

The Budgets and Contracts which do not close before the successor project start (compare #373 on closure) are proposed as new successor project Budgets and Contracts.

• The user can exclude a Contract from the successor project. This sets the Contract end (visually, effective upon task execution) to the current project end. It also removes all Contract Budgets from the successor project.
• The user can exclude a Budget from the successor project. This sets the Budget end (visually, likewise effective) to the project end.

Every successor Budget and Contract will be permanently linked to its precessor.

• The current Project cannot be deleted before its successor. It can, however, be deleted normally whether or not it has a predecessor.
• The Budget / Contract cannot be deleted before its successor.
• The successor Budget / Contract budget net total cannot be edited, but is linked to its respective Budget / Contract left (net) in the current project. This must be updated when the current project is updated (by new imports or daily rate changes. An adequate database based caching mechanism is highly recommended.
• Linked Budgets can be deleted but not restored.
• Linked Contracts can (for safety reasons) only be deleted after deleting all linked Budgets.

Succeeds #99. Depends on #373.