Cleaner code
Fixing DRUP for var replacement
No need to specify added clauses are non-learnt -- they are by default
Oops, forgot to add closing ' 0' to DRUP output
Simplifier class now seems DRUP-ready
Add pseudo-defintion in case we need to debug DRUP
Cleaner code
Fixing DRUP for Simplifier's strengthening
Don't sum up activities after replacement