Move pQCT_Testing.ijm macro to new directory

Hi Timo,

Just moving the testing macro into a new directory called macros. Not sure how we could best deal with macros in general. I was thinking that users might write their own and submit them to GitHub, but not sure how best to distribute them. Maybe just point here, as an online repository? Or else make a BoneJ-Macros project with user macros, which anyone could check out into their macros directory.

What do you think?

Michael