Improvements for documentation of top-level config file (`config.iesopt.yaml`) needed

[GerhardTotschnig]

@sstroemer Presently the input fields for carriers, connections, decissions, nodes, profiles and units are available at: https://ait-energy.github.io/iesopt/pages/reference/yaml/index.html https://ait-energy.github.io/IESopt.jl/dev/pages/manual___reference/api/

Good would be to have additionally a documentation on:

1. The first block of the iesopt.yaml: the config block.
2. A list of default settings for the config block would be needed. In exmaple 04 of IESoptLib.jl it is mentioned that parameter _constraintsafety is true by default. A list of deffault vaules for this config block is important.
3. Example iesopt.yaml with all the possible sections and keywords (addons, templates, ...)
4. Explaination of the rules for the iesopt.yaml. Order of the blocks important or not? Naming convention. How to find the default values?

[sstroemer]

Some reworks as part of ait-energy/IESopt.jl#20 should fix this (for the most part) soon:

• General notes can be found in the YAML section
• The top-level config has a new docs section (a few entries still need to be written, but it's 90% done)
• And the component (Julia) docs are now also accessible directly in the core component doc (the math rendering requires some fixes, but the main stuff is there - meanwhile the IESopt.jl docs render it correctly)