Update examples to match compiler output.
Keep just one, canonical heat equation example.
Modified twophase example with units.
Rewrite constants in example for readability.
Add missing comparison operators for backend.

Also reorder existing ones to have a sensible order.
Update output to match updated examples.
Remove some obsolete examples.

Also remove example output.
Update example output after changing example.
Fix example to account for units.
Use explicit list of non-dimensional examples.

The examples listed will be compiled with the --nondimensional option.
Merge pull request #35 from atgeirr/fix-examples

Fix examples