I have rewritten scripts/unembed-icons.py (now named unembed_icons.py), in order to fix #2375.

Right now only the basic functionality works (see gained features), but it is in an operational and maintainable state. I opened this pull so anyone who wants to contribute (especially to the TODOs in the code) is welcome.

Gained features:

• works on all mime-types (not only PNGs)
• it can automatically select a matching icon file from in the repo
• you can choose the location and filename of the extracted icon file
• does not mess with the formatting of the GeoJSON file
• better file selector interfaces

Lost features:

• operates on multiple GeoJSONs (TODO)
• fully usable in the terminal (TODO)
• adjustable log-level (TODO)
• colored logging (TODO)
• logs the space saved (easy to add, but not important)