Make uBLAS Expressions Move-able and Copy-able #49
Description
Old uBLAS Expressions (Vector and Matrix Expressions) are a reason why we cannot use many new utilities such as ublas::apply and optimization transforms. My current implementation for tensor-expression uses YAP where we can copy and move expressions giving us the ability to pass expressions just like normal objects. These functions can optimize and or make the expression more usable and can give the end-user more fine-grain control over the expressions in a nice and simple interface like ublas::apply
Proposed Change to the ublas expressions is will make tensors fully interoperable with ublas types and expressions. At the same time, we need to make sure that these changes are backward compatible as ublas is surely widely used.
Current;y, We fail a static_assert incase end-user tried to use ublas expressions with above-mentioned utilities directly or even indirectly (ublas expression wrapped in YAP terminal).