Fixed recently introduced bug in spacer rendering
Add %colwidthleft as a size spec
Weaken a reference, hopefully improves memory management
Minor comment cleanups
Fixed a typo in calculate_size
Wrote and switched over to Prima::Container for basic containers.

Two-column was getting annoying, so I finally go around to fixing it
with this new container class. Actually, the module includes
Prima::Container and Prima::GroupContainer, which are meant to be
drop-in replacements for Prima::Widget and Prima::GroupBox,
respectively, but with nicer packing.
Fixed container default pack handling.

The default container packing was being used even if the widget
had a place specification. Those two fought each other and led to
incorrect placement. This fixes that.
Bullet rendering now uses Prima::Container
More work on container rendering
Fixed handling of slide font_factor
Fixed bug in plot packing
Improved container-got-hash error message
Fix container stashing bug
Improve spacers to work for both x and y spacing
Streamline bullet rendering
Added spellchecking!!

I am so horrible at spelling. This will let me write some useful
mechanisms for ensuring that I don't write garbage! :-D