[Feature Request] Allow printing of encoded json rather than have to write it to file first

[tsurdilo]

currently --output_filename flag is needed for tctl wf show in order for tctl to encode history with JSONPBIndentEncoder.
allow similar way to print the results rather than having to save them to file.

for "version next" there is an -output flag but when setting it to json it does not print history json, and I'm not sure what it actually prints, just fyi.