Merged - Changes Helpful for Integration of Starcross Gallery into another site

[zoltan-ky]

Hi Alex, here are the pared-down merged list of changes in my fork for integration into sailboatdazzle.com. Long delayed, because I had to find the time and focus to disentangle and undo some of many cosmetic changes and additional changes in Image/Album management, but now these changes in 'merged' are minimal relative to your most recent master baseline. The changes are grouped into four independent branches in my fork included in this 'merged' branch:

1. Image.date_taken DateTimeField that is initialized from exif DateTimeOriginal if available, else the upload time. This allows django queries to select subsets of images. Added the import of 'piexif' that I found convenient for exif info access. A computed 'size_str' Image admin display column is also added for the usual width x height info.
2. Album.published. BooleanField that is set by admin after all the images have been uploaded and arranged/assigned to an Album. It can also serve for admin-private Albums used in support of some individual site pages
3. template_refactoring: Created templates/partials/album.html to allow its inclusion/reuse in more than one template location
4. js_clean: This is cosmetic but aids comprehension as it emphasizes that cursor is an argument and local within load_images_from_cursor(cursor) and a return value for the 'global' scroll_cursor.

Take a look when you can and let me know any questions/comments. We can then see if you're interested in a few more 'improvements' like cleaning the cache as well on image deletion, etc. Best regards!

[zoltan-ky]

Ok, so I see test coverage decreased warnings, but that's to be expected. I can add more tests related to these changes once it's known what will be accepted and merged.