Take actual regular expressions as input for the regex router rule

[joachimvh]

As discussed in https://github.com/solid/community-server/pull/283#discussion_r514614617, it would be nice if the regex router rule could have in its constructor storeMap: Map<RegExp, String> | { [regex: string]: ResourceStore }, with Components.js only taking the second part (since it's impossible to support the first part) of the union. This would probably require a drastic change in Components.js though. Maybe there is also a solution possible with different constructors or some other type magic instead.