2-stage dynamic_load_and_calc

[lentinj]

Currently dynamic_load_and_calc is a bit of a mess, and struggles to know what nodes need re-calcing, and then which parent nodes need recalculating.

Change the process so that:

• Newly created nodes are marked as needs_recalc along with parents, until a node already with the mark is found
• All projection methods follow the needs_recalc markers when recursing, rather than doing everything
• Once done, clear the needs_recalc flags (again, can follow any set flags).

The recursion could also be picked apart so that it only happens once.