[devel] OpenSoT::AutoStack issue with Bounds size

[arocchi]

as of now, creating an AutoStack with the usual MoT syntax:
auto_stack = (task1 + task2 / task3) << bounds;

will require an
auto_stack->update(q)
before being able to use the bounds via
auto_stack->getBounds()
since now the bounds are created during auto_stack creation instead of during the call of getBounds()
also related with #28 - maybe we could just make AutoStack a friend of Aggregated and call generateAll() when calling getBounds() ?