Enhance plugins and security modules

[burbas]

Before a plugin-function is called we check if it has arity 2 or 3. If it's 3 we include Env as the second argument.

This also introduce a mechanism to send replies to the caller by returning term of type reply() defined below.

-type reply() :: {reply, Body :: iolist() | binary()} | 
                          {reply, Status :: integer(), Body :: iolist() | binary() |
                          {reply, Status :: integer(), Headers :: [{binary(), binary()}], Body :: iolist() | binary()

Also enriches the return object from a security-module.

Instead of returning {false, Headers} one can now return three different options:

{false, Headers :: map()} |
{false, StatusCode :: integer(), Headers :: map()} |
{false, StatusCode :: integer(), Headers :: map(), Body :: iolist() | binary()}