Add generic directive/component for lightbox blocking message input.
Normalize lightbox behavior and implementation (styles, partial filenames, blocking message...)

- Normalize style clases names.
- Normalize partials files names.
- Normalize lightbox settings buttons behavior and implementation.
- Normalize blocking message input handling on userstories and tasks.
Minor code style cleaning at kanban/main.coffee file.
Merge pull request #12 from taigaio/bugfix-taskboard-lightbox-form

Lightbox improvements