Retire modules docs

[mabijkerk]

There is an outdated folder called 'modules-docs' on this repository. We should retire it.

• Check if any of the modules docs should be transferred to the 'standard' documentation pages
• Check if any of the 'standard' documentation pages still refer to the modules docs and update links when necessary
• Delete the modules docs

@kaskranenburgQ is this something you can pick up?

[kaskranenburgQ]

The modules-docs consists of 3 folders:

Assesment of files:

• local-datasets
  This folder contains a README.markdown file, this file describes how one could create their own custom datasets.
  It describes the 'scale' rake task, which can be used to scale datasets based on the number of inhabitants.
  It also describes the working of an excel script that can be used to achieve the same goal.
  If I recall correctly we have deprecated the function to create local datasets in the model, we can still keep the file for documentation purposes of the files that are mentioned in it. If we don't support the creation of local datasets any longer I propose we retire the file.

• Merit
  This folder contains a README.markdown file & a profiles_how_to.md file.
  The README is a shortened version of the file docs/main/merit-order.md, therefore this can be retired.
  The profiles_how_to.md file gives a small overview of how curves for renewable generation should be generated. It goes into greater detail on why the curves should not cause a conflict in installed capacities (Curve causes the output on a certain timestep to be greater than the installed capacity). This issue is outdated since we now use capacity profiles for the renewable supply curves, this issue does not exist with these curves. Therefore this file can be retired as well.

• multi-year-charts
  This folder contains 1 README.markdown file & a lot of pictures that are being referred to in the .markdown file.
  The README file contains an introduction to the Collections (former Multi year charts) tool in Dutch.
  Since there have been some changes lately with this tool, the documentation has become outdated.
  We could translate this documentation to English, and put it in the regular documentation.
  Update documentation about Collections #214 is related to this.

None of the files are being referenced to in any other files.