new app to create image pairs; in progress

[pearcetm]

This PR

• Updates the project homepage
• Adds a new demo page/web app that allows creating pairs of images with known transform offsets, for use in training algorithms for tissue alignment
  • The demo page is not self-documenting yet and is not necessarily intuitive
  • The offsets need to be converted to pixels still
  • The image pairs can't be easily downloaded yet