Fix config and prediction revamp. (#259)

Extend single_test_optimization.py to be able to use real world data from new prediction classes.
- .venv/bin/python single_test_optimization.py --real_world --verbose
Can also be run with profiling "--profile".

Add single_test_prediction.py to fetch predictions from remote prediction providers
- .venv/bin/python single_test_prediction.py --verbose --provider-id PVForecastAkkudoktor | more
- .venv/bin/python single_test_prediction.py --verbose --provider-id LoadAkkudoktor | more
- .venv/bin/python single_test_prediction.py --verbose --provider-id ElecPriceAkkudoktor | more
- .venv/bin/python single_test_prediction.py --verbose --provider-id BrightSky | more
- .venv/bin/python single_test_prediction.py --verbose --provider-id ClearOutside | more
Can also be run with profiling "--profile".

single_test_optimization.py is an example on how to retrieve prediction data for optimization and
use it to set up the optimization parameters.

Changes:
- load: Only one load provider at a time (vs. 5 before)

Bug fixes:
- prediction: only use providers that are enabled to retrieve or set data.
- prediction: fix pre pendulum format strings
- dataabc: Prevent error when resampling data with no datasets.

Signed-off-by: Bobby Noelte <b0661n0e17e@gmail.com>

tests/test_elecpriceakkudoktor.py

@@ -25,7 +25,7 @@ ems_eos = get_ems()
 @pytest.fixture
 def elecprice_provider(monkeypatch):
     """Fixture to create a ElecPriceProvider instance."""
-    monkeypatch.setenv("elecprice_provider", "Akkudoktor")
+    monkeypatch.setenv("elecprice_provider", "ElecPriceAkkudoktor")
     return ElecPriceAkkudoktor()