Provide first complete module integration workflow

[jnnr]

Here, I provide the first full module integration workflow that builds, solves and post-processes an electricity model at flexible resolution.

Core features:

• Rules handle input and output to each of the used data modules
• Rules in 2_prepare.smk convert the data format, scope and units to meet the requirements of Calliope models
• Templates in template_components can be parametrised using a templating class that allows to combine different custom_math, model_config and override templates.
• Model results are postprocessed 1 by 1 or in batch with the help of a Postprocessor and any number of Processor instances.

Areas for further improvement

• Cleaning up and potentially outsourcing and trimming down parts of lib.
• Further generalising the templating class.
• More extensive use of schemas in prepare steps.
• Keeping all data in parquet format as long as possible, potentially to the end if Calliope can handle parquet in the future.
• Clean up dependencies by introducing more environments under envs/