Use icons from FontAwesome

[php-coder]

Bootstrap 4 drops Glyphicon support and we should be ready for that. Let's start use FontAwesome.

Related links:

• https://github.com/FortAwesome/Font-Awesome
• https://scotch.io/bar-talk/whats-new-in-bootstrap-4
• https://dev.to/weeb/font-awesome-guide-and-useful-tricks-you-might-ve-not-known-about-until-now-o15

[php-coder]

At least we could use the following: user-plus, rub, use, eur, sign-in, sign-out

[php-coder]

Related issue for Bootstrap 4 migration: #1209

[php-coder]

There is also https://icons.getbootstrap.com that is available now and that will be used in Bootstrap 5