(cmake branch) Operations with integer numbers

[wavepacket]

If you write something like the following:

RTensor x = RTensor::random(5);
RTensor y = 2*x;

You get a compile error. The underlying reason is that the multiplication operator is only defined for floating-point values.
This is not a major issue, you could write something like "2.0 * x" to circumvent the problem, but somewhat surprising, and, thanks to the indecipherable nature of C++ error messages, moderately time-intensive to figure out.