WIP: support multiple images

Closes #132

Tested and it works as expected, also ran the ./run_tests.sh.

Example of usage below

--image-map       Find and replace image names per container according to a map. Overrides --image
                  Format: [image_str_contains1],[image1];[image_str_contains2],[image2]
                  Examples: ubuntu:18.04,ubuntu:20.04;nginx:1.18.0,nginx:1.19.9-alpine
                  Replaces all images that contain "ubuntu:18.04" with "ubuntu:20.04" and all images that contain "nginx:1.18.0" with "nginx:1.19.0-alpine"

This is a Work In Progress (WIP) since I've also added the --dry-run to be able to test it locally. Still haven't decided if I want to keep it in this PR

hello @unfor19 I think we were working on related stuff recently!

I prepared a PR for having the --image being applied on the main container image's only (where main means the first one). see #227

I think those can nicely live side by side anyway 👍 @fillup any feedback on this?

Given the age of this PR and that it has conflicts, I'm going to close it out. If you still want to pursue this, please submit a new PR based on the latest code.