Order horizontal piping correctly between buildings

[vtnate]

Any background context you want to provide?

Previous code had the correct total length of horizontal piping, but placed them incorrectly between the buildings.

What does this PR accomplish?

Use loop_order file generated by ThermalNetwork to determine the correct order of features, and assign the pipe lengths according to that.

How should this be manually tested?

On develop branch:

1. Generate a model using the test_district_multi_ghe.py file (no need to simulate)
2. Review horizontal pipe length list in Modelica model (lDis in tests/model_connectors/output/district_multi_ghe/District/DistrictEnergySystem.mo), which are in meters
3. Convert meters to feet, and compare the first pipe length with line 1494 of the geojson
4. Save the lDis output to compare with this branch

On this branch:

1. Same thing

What are the relevant tickets?

Resolves #674

[JingWang-CUB]

Looks great! I look forward to using this new feature.