“If costs are awarded on an indemnity basis, in many cases there will be some implicit expression of disapproval of the way in which the litigation has been conducted, but I do not think that this will necessarily be so in every case. What is, however, relevant at the present appeal is that litigation can readily be conducted in a way which is unreasonable and which justifies an order for costs on an indemnity basis where the conduct could not properly be regarded as lacking moral probity or deserving moral condemnation”