Database images aren't cached, add cache control

[jonespm]

I noticed that images that are loaded from the database aren't cached. This is going to put unnecessary load and extra traffic on us with every request

I found this thread here about how we can pass headers along to this url.

TEST PLAN:

• In Chrome, open View->Developer->Developer Tools->Network tab
• Launch CAE tool
• Verify the Size column list the image sizes for CAE tool log images
• Reload the page, now verify the size column shows (memory cache) for those image files

If a new image is uploaded the name is changed, so I think this caching for this default recommended year is fine.

[ssciolla]

I can QA this.

[zqian]

verified the LTI logo images are cached.