Provide a consistent base plot config pool and improve documentation

This MR removes some deprecated PlotManager arguments (see #260 (closed)) and adds the dantro/cfg/base_plots.yml file with the dantro base plot config pool.

It also expands the docs to showcase the separate entries, make them linkable, and adds a plots example page that shows how to use some of the base configs.

In addition, there are some tweaks and bugfixes:

• Add the .coords.transform data operation
• Fix a bug where set_ticks did not set ticks if arguments were given in shorthand form
• Add autofmt_xdate figure-level plot helper
• Expands the PlotManager by adding the shared_creator_init_kwargs argument, which can be used to set things like exist_ok on all plot creators.
• Adds a plots example page (#201 (closed))

Can this MR be accepted?

• Implementation ready
• Tests added or adjusted
  • Removed tests for deprecated arguments
  • Integration into PlotManager
  • Added tests that make use the dantro base plot config pool
• Documentation extended or updated
  • Docstrings
  • Separate reference page for dantro base plots
  • Example usage in plots, including output

• Code quality
  • Changes follow coding guidelines
  • Checked code coverage on new and adjusted code

• Ready for merging
  • Pipeline passes without warnings
  • History cleaned-up or squash option set
  • Changelog entry added
  • Version number bumped
  • Reviewed & approved by @tgaskin

Related issues

Closes #307 (closed), #260 (closed)