Refactor ContentFormat Class to make it know which usage is supported.

[sbernard31]

ContentFormat class should be refactor to move the knowledge of what is doable by each format.

The idea is to be able to request on a ContentFormat object if it is able to handle a given usage.

List of usage :

• single value
• multi value
• empty instance
• unknown instance id
• timestamped value

So in the code we would be able to check if a ContentFormat is suitable to a usage with something like:

if (!contentFormat.support(Usage.SINGLE_VALUE)) {
   throw new IllegalArgumentException();
}

This should help to add new content format.