Feature: Calculate emissions from servicing equipment time distributions

[RHammond2]

This PR adds in Metrics.emissions(), which will aggregate the time and distance traveled associated with transiting, maneuvering, idling at site, and idling at port and multiply it by user-provided emissions factors to calculate a total emissions breakdown.

See the CHANGELOG and documentation for details.

Co-authored by @hemezz

[codecov[bot]]

Codecov Report

Merging #99 (908e854) into develop (2f36334) will decrease coverage by 0.42%. The diff coverage is 20.93%.

@@             Coverage Diff             @@
##           develop      #99      +/-   ##
===========================================
- Coverage    54.98%   54.57%   -0.42%     
===========================================
  Files           21       21              
  Lines         3472     3500      +28     
  Branches       704      709       +5     
===========================================
+ Hits          1909     1910       +1     
- Misses        1448     1473      +25     
- Partials       115      117       +2     

Impacted Files	Coverage Δ
wombat/core/mixins.py	63.01% <0.00%> (ø)
wombat/core/port.py	17.08% <0.00%> (-0.22%)	:arrow_down:
wombat/core/post_processor.py	6.23% <10.71%> (+0.03%)	:arrow_up:
wombat/core/repair_management.py	68.37% <33.33%> (+0.33%)	:arrow_up:
wombat/core/environment.py	77.73% <50.00%> (-0.31%)	:arrow_down:
wombat/core/service_equipment.py	60.33% <57.14%> (-0.04%)	:arrow_down: