Replace `:` with ` ` in type annotations.

[python-processing-unit]

Currently, type annotations require a semicolon : between the type and the name, and allow any amount of spaces.

No longer allow any character beside space between the type and name in type annotations. Require at least one space between the type and name in the type annotations.

Update the signatures generated by SIGNATURE to follow the new type annotation form.

Update the implementation, specification, test suite, and standard library for this.