Positioning of extensions
=========================

How about using the alignment flags (or similar) for position, and the
direction flags for how to fill?


 ---------------
 |a    b      c|
 |             |
 |             |
 |             |
 |e           d|
 ---------------

a = Left | Top
b = Middle | Top
c = Right | Top
d = Right | Bottom

Now here's the filling

12345	   LeftToRight
54321	   RightToLeft (eg. for a right aligned thing)
5
4
3          BottomToTop
2
1


etc. etc.

Essentially, this splits the concept of positioning and layout. Now, lets get
crazy:

Imagine we're in position a and want to have a triangular corner layout:

1247
35
6

So, maybe we need some sort of concept of (one of):
 1) multiple linked rectangular blocks
 2) extensions/bars with a mask
 3) each item being considered independently (maybe some sort of magnetic
 blocks so they can be draggable?)

Finally, let's get really insane:

positions a AND c

12       65
34        7

This perhaps indicates that the details of placement should be passed off to
the extensions, but also that extensions might be 'linked'. eg. removing the
extension in position a should also remove c (and the configurations are also
linked).