The CC: and BCC: fields are not templated in EmailOperator #344

Describe the feature
There is no support for templated fields in CC: and BCC: fields
Only the 'to', 'subject' and 'html_content' fields in EmailOperator are templated.
In practice this covers all fields of an Oozie email action node apart from cc and bcc.

Therefore if there is an EL function in the action node in either of these two fields
which will require a Jinja expression in Airflow, it will not work - the expression will
not be executed, but rather treated as a plain string.

Expected behavior
The EmailOperator should be updated to support templating in those fields.