Custom node updates

[maartenbrinkerink]

Description

Changed the logic of the application of the data in resources/data/custom_nodes.

• ALL data in resources/data/custom_nodes will overwrite the data pulled from other sources in the main workflow (e.g. from PLEXOS-World) disregarding whether the nodes_to_add parameter is defined or not. Previously input files were only called if the nodes_to_add parameter was defined in the config file.
• Previously the application of the input files from resources/data/custom_nodes was inconsistent. E.g. for some input files only the data was pulled for new nodes that were defined in nodes_to_add (e.g. resources/data/custom_nodes/residual_capacity) whereas for others ALL data was applied including for existing nodes (e.g. resources/data/custom_nodes/RE_potentials). In this update the default is that ALL data that is defined in the folder will overwrite the base data.
• Related to the above, this means that not only data for custom nodes can be added but also data for existing nodes. Hence the custom_nodes folder has more or less become a custom_data folder.
• It is important to know that if data is added to resources/data/custom_nodes for nodes that are not within the geographic_scope or nodes_to_add it will trigger a fail of the workflow. This is deliberate as it is up to the users to define custom data. Having existing custom data (e.g. legacy data from TZ) without proper description is not something we should want.
• Fixed a bug that dropped values from TotalAnnualMaxCapacityInvestment within the storage rule.