"total energy usage" bug fix - excess-flows were removed from the summation, because this caused a double consideration (source + excess)

Fixed version of pyutilib added, because oemof.solph in the used version is not compatible with the new version pyutilib 6.0.0

branch test

See merge request !1

program_flow.pdf-> program_flow.png

Removed Typo.

bug fix: removing formatting errors

bug fix

Adding the transformer and link functions.

Adding description of the sink functions.

bug fix: repair hierarchy

bug fix: repair hierarchy

Adding description of the source functions.