Support utf-8 input and output in the shell

Also add --strict_unicode option which controls whether invalid unicode
code points should be ignored on input.

Change-Id: Ice59d6dd3df4557ab3b1fc91d7ddc0e1bf03f1c7
Reviewed-on: http://gerrit.ent.cloudera.com:8080/3394
Reviewed-by: Henry Robinson <henry@cloudera.com>
Tested-by: jenkins