Define language: British or US English

So far, we're using British English, both in the ECA Guide as well as in code - as much as we can.

Now, @michaellenahan stated in !121 (comment 301109)

even though I am in fact British, I like to use US English for documentation, because I am a big fan of consistency, but it's fine also if you prefer to stay with British English

I'm surprised because I thought British is the only real English ;-)

However, I'm open for a change here, since I also had realized in the ECA code that e.g. the spell checker on d.o is of course checking for American English. And therefore, our code is probably not even following our own rules any longer.