Create a facility for managing figures and generating labels based on where they are referenced etc.

[michael]

Much like the Bibliography module. E.g. we could call this a FigureColleciton.

Challenges:

• define what should be part of the index.
• we could consider tables also as figures, but they are labelled separately (Table 1 vs Figure 1) so we need different counting scopes.

@oliver---- thoughts?

[michael]

Will try to generalize this into a Collection interface, that we can subclass from:

• Bibliography
• FigureCollection
• TableCollection

[michael]

Done.