Add State field to Project Stages

This module brings back a State attribute on project stages, which lets you group the many stages of different projects into a few broad categories.

• On each project stage (Project Stages configuration), you can now choose a State among New, In Progress, Pending, Done and Cancelled.
• On every task, a State field is shown on the task form and is automatically filled from the stage the task is in. It is stored, so it can be searched and grouped.
• In the task search view, a State filter and a State grouping option are added, so you can quickly list or group tasks by their broad state.

This is useful when you want to apply automated actions or business logic to tasks that are, for example, not yet started, even though the exact stage names differ from project to project.

The module touches the project task and project stage models (project.task and project.task.type). It also adds access rights so regular employees can read and modify stages, while project managers can create and delete them.