Number Jam native type.

[grafikrobot]

• [ ] Add literal typed value parsing. Something like 12345.56:n to parse as a number.
• [ ] Add value coercion to Jam to be able to create specific typed values. This could look like $(X:n) to interpret the variable as a native number (i.e. a double). And $(Y:s) to get the string representation of the Y variable.
• [ ] Document.