Reivsed PT simplification. Solver issues pending.

src/topupopt/problems/esipp/converter.py

src/topupopt/problems/esipp/dynsys.py

src/topupopt/problems/esipp/network.py

src/topupopt/problems/esipp/problem.py

src/topupopt/problems/esipp/resource.py

src/topupopt/problems/esipp/time.py

tests/examples_esipp.py

tests/examples_esipp_network.py

tests/examples_esipp_problem.py

tests/test_all.py

tests/test_esipp_converter.py

tests/test_esipp_dynsys.py

tests/test_esipp_network.py

tests/test_esipp_problem.py

tests/test_solvers.py