Fix #1103, #1057

[dimitri-yatsenko]

• Fix .parts not always returning parts #1103 - Dependencies are now loaded in table.parts()
• Fix unite_master_parts breaks topological order of descendants and thus breaks cascading of table drops #1057 - Nodes are now topologically sorted, regardless of parts.

[ethho]

@dimitri-yatsenko Do you want help writing pytests for topo_sort? Or should we just test manually for now?

[dimitri-yatsenko]

topo_sort is already tested by multiple unit tests since it's used in several places. We can add more tests, of course.

[ethho]

Minor changes