Rewrite the non-React RingOverlay into the React Component CallOverlay
in a way which makes it easier to port to React Native.

We seemed to be using the names "film strip" and "filmstrip" (and,
consequently, their source code-conscious forms such as film-strip,
FilmStrip, etc.) In order to comply with our coding style which requires
a consistent one name for a given abstraction, choose one name and
rename the uses of the other name.

Wikipedia has a definition of a "filmstrip", I couldn't find a "film
strip". I guess our abstraction can be seen as what's described there.
When I google "film strip", I get results about "filmstrip" at the top.
That's why I chose "filmstrip".

Certain uses of "film strip" such as interfaceConfig.filmStripOnly and
in the external API I left untouched in an attempt to preserve
compatibility.

I wasn't sure whether CSS was tangled in compatibility so I made a
choice and renamed there was well.

In this case makes more sense to have overlay frame included in every overlay instead
of abstract class that implements the overlay frame and have to be extended by every
overlay. In addition, mapStateToProps isn't working well with inheritance.

Split language detectors to be web/native dependent. Take care of strings that contain html.