proj: configure items statuses

[silopolis]

• Create items statuses/board columns
• docs: project items statuses docs outline and screenshots #51
• docs: proj: write items statuses docs #59

These allow for the following workflow :

backlog > To-Do > Design > Dev > Test > Docs > Review > Done

Nicely viewed on the project's Kaban board.
Note that tasks should be ordered by priority, top to bottom, for each status/column.

I believe this should allow for a decent tasks and issues workflow.
Not all steps are mandatory of course.

By default, tasks/issues are added to backlog (no status) before they are planned for current/next iteration.
Work in progress should be limited to what can be achieved during iteration.
Theoretically, only backlog and Done should be populated at the end of each sprint.

[silopolis]

Please review and close if that's OK for y'all