[Geany] how to activate block selection mode

[John Yeung]

Again, Enrico manages to hint at his opinion without saying anything
that could be considered negative. ;)  I appreciate this, but I
personally am going to go a little further and say that I think it's
kind of sad that Geany would add clutter to its documentation because
other editors made a bad choice of terminology.

Since "block" can (and should!) mean other things to programmers, I
much prefer to the terms "column mode" and "rectangular selection".
These are much clearer and more direct.  It's harder to misinterpret
them.  And actually all the editors *I* have used call it one of those
two.  (Granted, there are many editors I have not used.)

If Lex wants to be nice and add it, then I guess it's really no skin
off my back.  But I still think it's a little sad.

John