Remove proto_item_append_text calls in favor of BASE_UNIT_STRING.

Remove proto_item_append_text calls in favor of BASE_UNIT_STRING.

Many proto_item_append_text calls were just adding a unit string to a field.
There's a better way to do that now.

Change-Id: Id18d5ac1ea4d8ecdc4cbe7ebaec07fbd2eab6e78
Reviewed-on: https://code.wireshark.org/review/19289
Petri-Dish: Michael Mann <mmann78@netscape.net>
Reviewed-by: Michael Mann <mmann78@netscape.net>