Release v0.5.1

Changed

• Remove performance bottleneck during NetworkPolicy computation in the Controller: add namespace-based indexers to quickly determine which internal objects need to be updated when a Pod is added / deleted.

Fixed

• Fix implementation of deny-all egress policy (no egress traffic should be allowed for any Pod to which the policy is applied).
• Fix antctl segfault when kubeconfig cannot be resolved and print error instead.