Pollemission: computational tool for air pollutant emission factors from traffic

The main purpose of Pollemission is to compute air pollutant emissions due to road transport, following COPERT methodology.
This formulation is described in the EMEP/EEA air pollutant emission inventory guidebook, the version 2019 of which was used (https://www.eea.europa.eu//publications/emep-eea-guidebook-2019).
The vehicle categories included are Passenger Cars (PC), Light Commercial Vehicles (LCV), Heavy Duty Trucks (HDT), Buses (Bus) and Light Category (Lcat) for the two wheelers.
For each vehicle category, an eletric type has been added to consider them for the wear emissions.

Main features:
- Compute emission factors [g/km] for different vehicle categories for several air pollutants: CO, NOx, VOC, PM, CH4 and NH3.
- For a given street network, compute emission factors for each street segments.
- 2 types of emissions are implemented :
    + Exhaust emissions both under hot running conditions and under transient phase (= cold) while the engine and the post-treatment have not reach their running temperature.
    + Wear emissions from tyre and brake wear, and road abrasion

Compared to the COPERT methodology that does not compute cold exhaust emissions of PM from the petrol PC and LCV, Pollemission uses a ratio compared to diesel vehicles to assess these emissions.