Improve rescaleCyc efficiency for Pow/Dec bases

[crockeea]

The current definition of (say) rescaleCyc Pow for a tuple in the Dec basis may convert the entire tuple to Dec basis. The offending code is (b - reduce z): reduce z would be in the Dec basis, while each b is in the Pow basis. It is up to (-) to determine which term gets converted. To ensure the most efficient rescaling, we should "adviseBasis" to attempt to put z into the basis of b (before reducing). This will make the case above more efficient, while not impacting the efficiency of rescaling a CRT input.