Update definitions of all anatomical axes orientations #333
Description
We have encounter some confusions while registering the marmoset atlas. Basically, it seems to be unclear that they refer to the orientation positive axes (i.e., the side of the axis where the values are greater than zero).
I would suggest to make our definitions more explicit to avoid this confusion in the future, e.g.:
Old RAS definition:
"X, Y, Z axes are oriented towards right, anterior and superior, respectively."
New RAS definition:
"The positive X, Y, Z axes are oriented towards right, anterior and superior, respectively (i.e., their values increase towards this direction)."