Introduce new emission-factor-based bioenergy tax

[merfort]

Purpose of this PR

This PR introduces a new type of bioenergy tax. The new tax is based on an emission factor (EF) that can be read in via a switch, which is deactivated by default. The tax itself is calculated by multiplying the EF with the carbon price, resulting in a price markup per unit of bioenergy. The EF only informs the tax level, i.e. it does not affect emission fluxes. It can be read in on a regional level. A detailed description of this tax is found in the description of equation q21_taxrevBio.

In order to distinguish this new tax from the already existing bioenergy tax, the old tax is renamed from cm_bioenergy_tax to cm_bioenergy_SustTax as it is justified by general sustainability concerns, whereas the new EF-based tax only accounts for potential emissions that should be internalized.

Summary of changes:

• Introduction of (region-specific) EF-based tax
• Renaming of original bioenergy tax to bioenergy sustainability tax
• Removal of p21_tau_bioenergy_tax, which was only used for reporting (the reporting was adapted accordingly)
• Minor bug fix in magicc reporting
• Code clean-up

Type of change

• Bug fix
• Refactoring
• New feature
• Minor change (default scenarios show no differences, since the switch is deactivated by default)

Checklist:

• My code follows the coding etiquette
• I have performed a self-review of my own code
• Changes are commented, particularly in hard-to-understand areas
• I have updated the in-code documentation
• I have adjusted reporting where it was needed
• The model compiles and runs successfully (Rscript start.R -q)

Further information (optional):

• Test runs are here:
  /p/tmp/merfort/REMIND_development/remind/output

• Comparison of results between different tax levels of the sustainability tax (sustTax...) and the EF tax (EFTax...), can be found in the following compare scenarios PDF:
  /p/tmp/merfort/REMIND_development/remind/compScen-TEST_SustTax_EFTax_all-2022-10-12_10.26.47-H12.pdf
  It can be seen that taxing bioenergy according to and EF of 20 kgCO/GJ has (on a global average) a very similar effect as if the sustainability tax is set to 1.5 in terms of bioenergy demand reduction (compare the two greenish lines):
  

[merfort]

After pulling develop and test runs failed. Need to check why...