Adding support for non-Google Street View panoramas

[dmbaty]

Summary

This adds support for non-Google Street View panoramas, and includes proper support for handling lower resolution panoramas.

Changes

• cli.py:
  • Added a check on image size. If high quality is not available (max width less than or equal to 8192), downgrade to medium automatically and print a console message indicating this change was made. Otherwise, a blank image is created. Continuing with a message feels more appropriate than stopping, especially if batch processing.
• core.py:
  • Added scale factor adjustment based on max resolution, as smaller panoramas will be cropped incorrectly otherwise. These panoramas don't have zoom 5 (high quality) available and this causes issues with scaling.
• metadata.py:
  • Search for only "!1s" instead of a longer string in URL to extract more panorama IDs, including those from non-Google panoramas. The longer string of "!3m5!1s" seems to miss non-Google panoramas (and perhaps others).
  • Added a check and conversion process to the format for non-Google panoramas. These must have a preamble added and converted to base64 to be passed to the API.

Notes

• Some of this was accomplished via reverse engineering, so testing on a wider range of non-Google panoramas may be required.
• The list of characters to identify non-Google panoramas may not be complete.
• This resolves closed issue Error: Could not extract panorama ID from URL #4, though some of the example URLs there do not work. The URLs may be malformed, as in a browser the image is shown but with an error.