Photos 1.3.0

• Add default processing information and pass them to the Pillow writer
• Fix issues with multiprocessing
• Add option to detect number of CPUs
• Add new class to hold information about the source image
• Add caching for exif, notes and exclude lists
• Add high and width information from the result image
• Update signal and config handling
• Add optional api documentation
• Add more docstrings
• Add an initial version of an example blog to show how to use the plugin