Enforce tighter restrictions on folder + module name

[Bartvds]

From DefinitelyTyped/DefinitelyTyped#1565

Could be fun to apply, but needed for sanity. Especially spaces etc.

Probably like /^[a-z]([_.-]?[a-z0-9])+$/

(I'm so annoyed by the definitions for Finch that have uppercase and somehow sort to top of DT repo.)