Extract Component config functionality to a separate class

[GeoSot]

As we use the config functionality in many places, we maybe can use it extending a base Config Class

[GeoSot]

@twbs/js-review
I need some help here.

After some discussion I have concluded to the following.

Config can be three different things:

• An abstract with mutable getters (as it is now on Tooltip|Popover, and can be changed by developers)
• An abstract with immutable getters (private methods)
• A separate Class|object that any component can initialize

The third option seems to be more strict (and with some difficulties on its implementation)
Both first and second are very close too our existing codebase.
IMO the first is ok as we give the opportunity to devs that use Bootstrap to extend/change some Defaults on the fly, with the second to be a more professional choice than first, as it can give the same freedom, only after extending a class that already extends the Config abstract (better for third party plugins and custom impersonations)

Any opinions are welcome

[rohit2sharma95]

So choosing the first option seems good, but the APIs should be kept private initially IMO. Since that's the fully internal thing.