Allow to introduce new (custom) states, therefore enhance kanban board

This might allow a better use of the kanban board when tasks requires more granularity.

Maybe allow to name some progression state, like threshold. Eg: 10% -> discussed 15% -> validates

Drawback, it ends up being quite limited (so much state, lack of reorder)

Another option would be the other way around: create other states equivalent to prgression (as suggested elsewhere) Eg: 'to be implemented', an alias of todo discussed, an alias of 5%

But relationship task/state should be on the custom state to allow changes like its label and or associated attributes like color or progression %, virtually applying it to all tasks in this very state.