Refactor the card framework

[sbegaudeau]

The card framework needs to be re-organize with one component per file and we will need to rethink some of those components (do we really need a body and footer instead of more specific blocks?)

[sbegaudeau]

We should also properly define the API of the components with their propTypes. As an example, what kind of events should be available on ItemText? What kind of API should be available to WorkflowSectionCard and what kind of API should WorkflowSectionCard offer? (onClick, handleClick, etc?)

Define a proper naming convention for the events of our components.