Credits drain fix

[daschuer]

This removes the big background images causing 67 % Bandwidth and enables client side caching. This shall save ~15 € per month.

This is just a quick fix. On a long run we need a different solution.

[ronso0]

No banner makes the website look a bit boring.
Re-encoding the splashscreen to jpeg 85% etc. would already reduce size to 10% (83 kB vs. 805 kB)

[Eve00000]

The banner (and other static info like images) could also be placed elsewhere (not in netlify, eg downloadserver, or in a 2nd account)

[daschuer]

I know all that. But can we just merge this without the banner and look if it really saves 1 € per day?
If it turns out we are not able to reduce the credits spends near to the free threshold, all efforts for a better bandwidth safe solutions are mood. We will move to a unlimited Bandwidth host and fix the root cause, this is a better spend for our time IMHO.

[JoergAtGithub]

Tweaking the cache parameters is a good thing, but disabling the background image is not Ok. We can easily afford that little money until we switch to a webhoster with unlimated bandwidth.

[daschuer]

We are talking about ~15 € a month for displaying backgrounds for eye candy only. Not a good spend IMHO.