Bugfix in HalfEarth Scenario: Synchronization until 2020 with WDPA protection scenario

[FelicitasBeier]

Please fill following information
(Add additional info if you think its important and not covered by this Pull Request (PR)):

Purpose of this PR

• bugfix: synchronize HalfEarth scenario with WDPA until 2020, so that scenarios only diverge after 2020

Performance loss/gain from current default behavior

• performance gain = 0.623352/0.6361311 = 0.9799
• like already noted when the HalfEarth Scenario was introduced the first time: runtime is even a bit faster compared to default (WDPA protection)

Type of change

• Bug fix (Change which fixes an issue).
• New feature (Change which adds functionality).
• Minor change (Change which does not modify core model code i.e., in /modules).
• Major change (fix or feature that would change current model behavior).

How Has This Been Tested?

• Runs using starting script which tests current defaults (using test_runs.R).
• Runs using starting script which successfully runs the same scenarios as in test_runs.R but with the changes from PR.
• (If applicable) Runs using different scenarios/mappings which are not the default (12 regions/c200 clusters).

Additions or Changes to default configuration (default.cfg):

no additions required

Changes are deletion or updates to the existing model components in default config

• Realizations:
• Scenario switches:
• Scalars/Constants:
• Model interfaces:
• Others: only change in presolve (synchronize data before 2020)

Checklist:

• Self-review of my own code.
• Compilation check (model starts without compilation errors).
• Added changes to CHANGELOG.md (I think this is not required, since it was only a bugfix, right?)
• No hard coded numbers and cluster/country/region names.
• The code doesn't contain declared but unused parameters or variables.
• In-code comments added including documentation comments.
• Compiled and checked resulting documentation with goxygen::goxygen() for the new/updated parts.
• [] Changes to magpie4 R library for post processing of model output (ideally backward compatible).

Special comments/warnings

• Notes: It was only an adjustment when the HalfEarth protection kicks in

[abhimishr]

Looks fine to me. So WDPA is active till 2020 and then additional protection after 2020 with half-earth (WDPA+something). I'll approve it but would recommend waiting until @flohump also approves it.

[FelicitasBeier]

UPDATE: The HalfEarth scenario now fades in until 2050.
Also: Code-cleanup of the interest fader (now read in as csv instead of hard-coded section in the code)

[flohump]

One issue needs to be resolved in presolve line 76