new feature for Layout transformation: panel alignment and distribution

[pierrelabreche]

It would be useful to allow selecting panels for alignment and distribution:

• align panels left, right, center horizontally

• align panels top, bottom, center vertically

• distribute panels horizontally

• distribute panels vertically

[jsachs]

These are reasonable suggestions -- will add this to the requested features list for future releases.

[pierrelabreche]

Thanks !