Clear F keys

[bastianschwarz]

The F keys are bound to things we usually don't need and even worse: They prevent the default binding from PHP Storm from working (e.g. alt+F7 for usages or alt+12 for terminal).

The F keys should be cleared from any bindings

For gnome:

• https://community.linuxmint.com/tutorial/view/1171
• https://gist.github.com/fwilhe/2f1f1878113883535156e230cba62bed