held image status colored squares to native resolution

[tjslezak]

Tweak suggested by @pbvarga1

The colored symbols used to display the status of support for a given image-set in planetary image selectively resize on certain platforms. This is an attempt to hold the symbols .png to their native (fixed) size.

We won't be able to see if the fix works until this merge request is accepted.

[godber]

If we're going to spend time on this can we go find four matching icons of different color?

And I am pretty sure you can build the docs with Sphinx prior to me accepting it.

[godber]

Awesome icons!