Forward osmosis unit model and Trevi's system flowsheet #999

Job	Run time
Check code is formatted (Black)	10s
pytest (linux/3.8/editable)	11m 51s
pytest (linux/3.8/noneditable)	10m 40s
pytest (win64/3.8/editable)	19m 2s
pytest (win64/3.8/noneditable)	11m 22s
pytest (linux/3.9/editable)	12m 8s
pytest (linux/3.9/noneditable)	10m 45s
pytest (win64/3.9/editable)	19m 12s
pytest (win64/3.9/noneditable)	12m 32s
pytest (linux/3.10/editable)	8m 45s
pytest (linux/3.10/noneditable)	8m 25s
pytest (win64/3.10/editable)	19m 27s
pytest (win64/3.10/noneditable)	12m 49s
pytest (linux/3.11/editable)	7m 12s
pytest (linux/3.11/noneditable)	7m 32s
pytest (win64/3.11/editable)	14m 2s
pytest (win64/3.11/noneditable)	10m 58s
	3h 16m 52s

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