Image aspect fix

[ishaisagi-hns]

• New sample
• [ X] Bug fix/update
• Related issues: fixes #X, partially #Y, mentioned in #Z

What's in this Pull Request?

1. Major: Fix for aspect ration defaults (previous change was getting the checkbox to be selected by default, but the editing controls ignored it until the checkbox was clicked again)
2. Major: image upload was not implemented before. the new code will ensure a folder for the current page in the site's "Site Assets" library and upload the selected file to that folder.
3. added webpart settings that allow the page editor to determine what source of photos are allowed in the webpart

Node Version

8 or 10

Node version used:
8

• [X ] My pull request affects only ONE sample.
• My sample builds without any warnings
• I have updated the README.md file's Version history. For new samples, created a new README.md file matching this template
• My README.md has at least one static high-resolution screenshot (i.e. not a GIF) located in the assets folder.
• My README.md contains complete setup instructions, including pre-requisites and permissions required
• My solution includes a .nvmrc file indicating the version of Node.js