Add "cooling tower tons" to default units

[ellieLitwack]

Refrigeration tons are already included in the default units. In the HVAC industry a different unit, cooling tower tons, is used to measure the heat rejection capacity of heat rejection equipment like cooling towers. A cooling tower ton is defined as 25% higher than a refrigeration ton because chillers typically produce 25% waste heat which must also be rejected by the heat rejection equipment. Cooling tower tons should be included to better support developers using Pint to model entire chilled water plants and other systems including heat rejection equipment.

A few sources documenting cooling tower tons as a commonly used unit in the HVAC industry:
https://www.engineeringtoolbox.com/cooling-loads-d_665.html
https://www.baltimoreaircoil.com/what-is-a-cooling-tower (note that cooling 3 GPM (0.19 lps) of water from a 95ºF (35.0ºC) entering water temperature to an 85ºF (29.4ºC) requires 15,000 BTU/hour of heat rejection).
https://www.energytrust.org/wp-content/uploads/2017/03/BESF_Presentation_8.15.12_Part_1.pdf (slide 9)

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