Add arithmetic & related operations when unambiguous

I'd like to propose adding basic operations on intervals, such as multiplication by another value (the specific list of operations to be defined).
Multiplication is supported by different Julia objects, not just numbers. For example, arrays – and this is often convenient:
```julia
2 * [1,2,3]

using Unitful
[1,2,3]u"m"
```
I don't see any discussions of such a proposal before. What do you think?