Removed fatal termination from object constructors.
Implemented new KubeClient class with test method which creates a Secret.
Improved comments for the types structures.
Added WebhookServerConfig structure instead of the most parameters to NewWebhookServer.
Implemented checking of incoming request to correspond the policy rule, added tests.
Implemented generation of JSON patches according to patches in policy object, added tests.
Implemented base version of Mutate function as a wrapper for all mutation functions.