Revert "fix NaN comparison"

This reverts commit 9be3dffbb9046af498c0fc92accb0cb766126c0f.
Revert "fix NaN comparison, including null values"

This reverts commit f72d2cad9cfd180c2cc3558c02f71dbbd0f4b631.
Revert "using SemMF context matcher; added 0 as score to default situations"

This reverts commit 43f2551773c94362ef72be2f962544eea9164764.