Use unicode symbols instead of some minor images

[ultimate]

There are plenty of unicode symbols of which some may be usable instead of some drawn svg-icons, e.g.

• ✉ 📨 (✉ 📨) (as message icons)
• 🚀 (🚀) (as a troop movement icon)
• ✖ (✖) (as close icon)
• 👤 (👤) (as profile icon)
• ⚙ (⚙) (as settings icon)
• ☐ ☑ ☒ (☐ ☑ ☒) (as a check box)
• ⚔ (⚔) (as an attack icon)

e.g. see

• http://www.fileformat.info/info/unicode/block/dingbats/utf8test.htm
• http://www.fileformat.info/info/unicode/block/miscellaneous_symbols/utf8test.htm
• http://www.fileformat.info/info/unicode/block/miscellaneous_symbols_and_pictographs/utf8test.htm

Note: some symbols may be displayed as images here, since github supports emojis and markdown, but there are plain unicode versions of them, too!