Missing methods for UniTensor #681
Description
The following methods are available for Tensors, but not for UniTensors yet:
Abs
Min
Max
Exp
Mod
operator-() (without arguments, corresponding to sign flips of all elements)
Cpr (compare two UniTensors; this is in principle implemented in the unittests, but not available as a method)
They are useful and some are necessary for certain algorithms. It would be great to have them all (and the inline versions as well).