518.12 Instrument creating or defining powers, duties of fiduciary not affected.—Nothing contained in ss. 518.10-518.14 shall be construed as conferring a power of sale upon any fiduciary not possessing such power or as authorizing any departure from, or variation of, the express terms or limitations set forth in any will, agreement, court order, or other instrument creating or defining the fiduciary’s duties and powers, but the terms “legal investment” or “authorized investment” or words of similar import, as used in any such instrument, shall be taken to mean any investment which is permitted by the terms of s. 518.11.