bug in compare nodes

[gidden]

there appears to be a large bug in the compare nodes function. I can't isolate it with small test cases as of yet, but it came about as I was comparing inpro files. for some reason my expected inpro file had the recipes missing, but compare_nodes still returned true. I was actually able to gut the entire file except for the region node and have it still return true.

I've provided some tests in my branch test-compare-hotfix that currently fail but should pass. This will most likely require pretty extensive additional unit tests for different tree structure cases and a revisit of the comparison algorithm.