Disallow arbitrary file upload from js

[uuf6429]

In some cases we need to trigger a file upload from the page JS.

The JS running inside the browser is not usually allowed to perform this action (for obvious security reasons).

In our case, we need this functionality without opening a huge security hole. The solution is to have a whitelist of files that can be uploaded:

-> setValue(element, value)
-- allowedFiles = [value]
-- <- setFileValue(value)
-- if value in allowedFiles ...

Issue happens here: https://github.com/uuf6429/MinkElectronDriver/blob/master/src/Server/Server.js#L267