Consider renaming factories

[frederikbosch]

When developing this library, I really had a hard time picking the right names for the right jobs.

Especially the name FormattedMessageFactory is controversial. It is a factory in a sense that is producing messages: like it drops messages from the assembly line. Therefore I chose the name.

However, I also read people rather see it as a builder. That also makes sense. Maybe it makes more sense. Since the library is already in stable state, however, I will only consider changing the name in a new major release.

[frederikbosch]

Since this will be breaking, I will not go forward with it.