support exclude options when using "paths" for typings override

[Luca Looz]

We need to be able exclude some paths entries which are used to override typings.

e.g.

"paths": {
    "mymodsources*": ["packages/mymodsources/src"],
    "mymod": ["typings/mymod/mymod.d.ts"]
}

here we want to exclude mymod from webpack aliases so that it doesn't try to bundle a .d.ts file