Implement feature: settings - default layout and config values

[Dmytro-Shulha]

There should be an option to define default layout and config values in settings. Option to create several layouts and choose particular preset for each plot is nice from code reuse perspective.

Separated from #4

[Dmytro-Shulha]

If settings are going to support several layouts, each one should have a name, and there should be a way to select a preset layout for a given chart. For all charts in vault, it can be chosen by a radial button in settings menu. For all charts in directory, it can be configured in settings menu as some dir->layout mapping. For all charts in file, YAML frontmatter properties can be used. For a single chart, preset layout variables should be available to use inside chart block.