This commit adds the web report page and all the required changes to
show the page, among the most important changes:

- Add module to generate the report page
- Add web page index.html
- Update the webhook to show the page in the route
  /report/release/image_version
- Add script to generate the `test cases -> images` table
- Add initial test case table: tc_table.py
- Add css files
- Update README.md file explaining how to update tc_table.py

Signed-off-by: Luis Araujo <luis.araujo@collabora.co.uk>