Introduce LanguageFeatureSettings, instance of which should be injected by the
container and be accessible everywhere during the compilation (front-end and
back-end).
Parameters of LanguageFeatureSettings are unused in this commit, will be used
later
Following the rule of the least surprise: this option is named "-nowarn" in
other JVM language compilers. Besides, having an option with an argument which
can take exactly one predefined value is sort of confusing
Use free arguments instead, as is done in kotlinc-jvm and all sensible
compilers everywhere
Also fix some cases of AntTaskTest to be able to run them locally
Alexey Andreev