Clean up documentation files

[madmiraal]

Address multiple issues in the API XML documentation, the API RST documentation generation, and the API and editor translations including:

• Fixing the unwanted line-break and space in the documentation of an empty Dictionary default value.
• Fixing the API XML documentation generation tool not removing indents on multi-line entries.
• Fixing the XML to RST documentation creation tool not removing indents properly.
• Updating the Python shebang of the documentation status tool.
• As done in Apply Rebel coding style #19 (9c8daa9), replacing tabs with spaces in all documentation files.
• As done in Use SPDX standard headers for all code files #22, adding SPDX standard headers to all documentation and translation files.
• Using docs instead of doc when referencing multiple documentation files; including the documentation folders.
• Renaming the --doctool option to --generate-docs.
• Removing various unused documentation creation tools.

[DanielaOrtner]

Fantastic PR! The changes make the code so much clearer :)