Allow passing environent variables to StreamProcessors

Add support for an 'env' field to the StreamProcessor configuration
and append the environment variables found there to the os.Environ()
array.
The env field takes environment variables in the form of key=value.

Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>

diff/stream_unix.go

@@ -33,9 +33,10 @@ import (
 )
 
 // NewBinaryProcessor returns a binary processor for use with processing content streams
-func NewBinaryProcessor(ctx context.Context, imt, rmt string, stream StreamProcessor, name string, args []string, payload *types.Any) (StreamProcessor, error) {
+func NewBinaryProcessor(ctx context.Context, imt, rmt string, stream StreamProcessor, name string, args, env []string, payload *types.Any) (StreamProcessor, error) {
 	cmd := exec.CommandContext(ctx, name, args...)
 	cmd.Env = os.Environ()
+	cmd.Env = append(cmd.Env, env...)
 
 	var payloadC io.Closer
 	if payload != nil {