Create more annotations like @ParametersAreNonnullByDefault

[cushon]

Suggested by @Stephan202 in #93 -

If possible, I'd like for you to consider another annotation, namely @EverythingIsNonnullByDefault as defined in this SO answer or variations thereof, such as @ReturnTypesAreNonnullByDefault and @FieldsAreNonnullByDefault, as defined in this SO answer. It would do away with the need for everybody to re-implement/redefine these annotations themselves. (I used these in several internal projects, and based on the SO answers it's not uncommon for other to do, too.)

If error-prone starts checking nullness annotations we should consider adding these.