Introduce Date type

[nicosammito]

• Date -> type Date = number
• Month -> type Month = 'January' | 'February' ...
• Hour -> type Hour = number (range between 0 - 24)
• Minute -> type Minute = number (range between 0 - 60)

[nicosammito]

@raphael-goetz comment on functions you will add to the runtime supporting these types

[nicosammito]

Data types are done. I will hand over the issue to @raphael-goetz for functions