Original source of icons is the icon8 library (http://icons8.com/c/flat-color-icons) and Paomedia (https://github.com/paomedia/small-n-flat). All icons used are licensed MIT or CC0; annotated in COPYING.
* Closes #4071
* Increase default size of database icons to 24px and entry preview panel to 48px
* Add shell script to assemble the database icons
* Use QIcon to seamlessly support High DPI displays and pixmap caching
* Add badge support for KeeShare groups and expired entries.
* Guard against use of QPixmap::fromImage without a GUI
* Add SVG minify and improve `make icons`
Co-authored-by: Wolfram Rösler <wolfram@roesler-ac.de>
