Update the "Create content" page with the two content types

Apparently creating separate content types is a big thing, requiring custom function names for each content type. I had hacked the functionality by adding separate menu links, but this isn't the right way to do it. Eventually it will require a bunch of extra fixes, and potentially splitting the different modes into distinct .module files, which will facilitate better customization.

I was able to get this working by modifying decisions_node_info to show two content types (decisions-ranking and decisions-poll) but to have them use the same module basename for functions (decisions_*). So now each function figures out which type it is by examining node->type via _decisions_get_mode(). This is a big change that might have various hard to find bugs. See http://drupal.org/cvs?commit=42651

I should also be clear that this change will invalidate all previously created decisions.