added if statement to dog show page for img

[hellokatze]

sry for the late pull requests heheh

• added dropdown list of breeds in add dog form
• added if/else statement for image in dog show page so it shouldn't break there anymore
• slightly improved dog show page but it looks kinda boring....so maybe someone else has an idea to spice it up?
• added more text to the details for each dog seeded so it fills out the container on the show page.
• removed extra container that was wrapped around the add dog form (causing it to be uncentered on certain screens)