Enable NullAway errorprone checks (#2204)
Enable NullAway errorprone checks (#2204)

* Enable NullAway checks
* Default to warnings for now so we can fix nullability issues in a future PR
pkwarren/dropwizard,nickbabcock/dropwizard,micsta/dropwizard,tjcutajar/dropwizard,jplock/dropwizard,tjcutajar/dropwizard,micsta/dropwizard,phambryan/dropwizard,dropwizard/dropwizard,phambryan/dropwizard,mosoft521/dropwizard,jplock/dropwizard,jplock/dropwizard,Alexey1Gavrilov/dropwizard,mosoft521/dropwizard,Alexey1Gavrilov/dropwizard,dropwizard/dropwizard,dropwizard/dropwizard,pkwarren/dropwizard,nickbabcock/dropwizard,micsta/dropwizard,Alexey1Gavrilov/dropwizard,phambryan/dropwizard,pkwarren/dropwizard,tjcutajar/dropwizard,mosoft521/dropwizard,nickbabcock/dropwizard