Remove Fuel and EndUse columns from technodata files

[tsmbland]

Description

As explained in the issue, these columns are entirely redundant as this information can be determined from the CommIn and CommOut files. There were a couple of places in the code still using the information from these columns (namely the same_fuels filter and the LCOE/EAC outputs), so I've modified these to get the relevant data from the commodity flows instead (via the comm_usage field of the technologies). I've also modified the example models and documentation, and added a warning if technodata files still contain these columns (it won't break anything, but it's a good opportunity for users to simplify their input files)

Fixes #493

Type of change

• New feature (non-breaking change which adds functionality)
• Optimization (non-breaking, back-end change that speeds up the code)
• Bug fix (non-breaking change which fixes an issue)
• Breaking change (whatever its nature)

Key checklist

• All tests pass: $ python -m pytest
• The documentation builds and looks OK: $ python -m sphinx -b html docs docs/build

Further checks

• Code is commented, particularly in hard-to-understand areas
• Tests added that prove fix is effective or that feature works

[dalonsoa]

The changes look OK to me. The code looks marginally more complex, but it is the right move as it also avoids inconsistencies in the input files.