We do following changes to two small independet templates used
in stream_settings area:
* Move subscription_setting_icon.hbs to stream settings folder
to have a consistent folder structure for stream settings templates.
* Rename `subscription_count.hbs` to `subscriber_count.hbs`.
* Move `subscriber_count.hbs` to `stream_settings` folder.
m-e-l-u-h-a-n