Create an explicit stdlib

[AlexGustafsson]

There's a possibility that the current builtin mechanics will not scale well. Instead, create a stdlib where the imports have paths like std/io to use like so:

io::print("hello")

Perhaps some functions, such as print should be kept a builtin? Others, such as split, range etc. should perhaps not. They could even become a "property function" like in JS - "hello".split("\n"), Array.range(0, 2) etc.