Introduce @ParametersAreNonnullByDefault #539
Description
After a full year of writing @NonNull everywhere, we should move over to @ParametersAreNonnullByDefault and only annotate @Nullable, for parameters that is.
The annotation goes into all package-info.java files on each package. Here is a SO explaining how to do it: https://stackoverflow.com/a/7658232/2411243
It is okay if we integrate it step by step. For example first add it to all existing package-info.java, then removing all @NotNull on params in these packages and later converting packages that dont have a package-info.java yet (because someone was too lazy writing a proper package doc? 😄)
The advantage of this is clearly: Less boilerplate > less to read > easier to understand