fix false negative isuniform of transposed const
fix false negative isuniform of transposed const

The `isuniform` test currently responds with a false negative when the argument
contains a `Transpose`. This commit adds support for `Transpose` by peeling of
`Tranpose` instances of the argument in addition to `InsertAxis`, before
testing whether the argument is the desired `Constant`.

wijnandhoitinga/nutils