Include heat-related ReactorProtype properties in HeatEnergySource

[Thremtopod]

Make the functionality of ReactorProtype's connection_patches_connected, connection_patches_disconnected, heat_connection_patches_connected, and heat_connection_patches_disconnected available to HeatEnergySource.

When using a HeatEnergySource, it's very difficult to make the heat connections look nice. For ReactorProtype, the functionality is built in with these prototypes. Because it doesn't really make sense to have HeatEnergySource without heat connections, it should be easier to utilize this functionality.