Make compiler interchangeable again

[mariopesch]

To test different versions and compiler deployments we should make it possible again to change the compiler URL in the settings.

• Add compiler url as prop
• adopt setting page
• add prop to all relevant components
• remove compiler url from .env file

[Thiemann96]

So we have a setCompiler function which changes the compiler globally. i did not pass the prop for compiler to all components but rather just use the global variable. so slightly different than you described. let me know if that works for you and if i've missed something