Move the section insets to the layout itself, instead of per-section

The section should just fit itself into the frame it is given.
Add a method which will offset the header layout attributes (if needed) given a certain content offset
Variable name changes
Fixes an issue where the wrong substring would be parsed out
Add a view for the grid divider
Make sure the arrays are allocated when the object in initialized
Reduce a section's dependence on the layout reference
First pass at the full-height divider layout
Don't ask if a section has a featured item; just assume that if either the horizontal or vertical span is 0, it does not.
Use the correct constants
re-enable the featured section behavior
Fix the layout of the divider decorations in featured sections
Add a property to make it easier to determine of the row is filled or not
Add more comments to a few potentially hairy spots
Typo!
Add a property to track the featured state of the section
Fixes an crash when attempting to modify a nil header layout object
Ensure that even if there are no items in a section, the header should appear
Move the responsibility for laying out the decorations to the section helper
fix crashes due to attempting to add nil layout attributes to an array