- changed name of derive to diff and differentiate.
- changed the type of the realizers to take and return shared_ptrs.
- moved some of the usings around.
- added POWERSERIES.tpp and rep_powerseries.tpp to the makefile.
- fixed an issue where debug output lead the program to diverge when debug level was set to 5.
- fixed an error where the error of the approximation was not correct if the evaluation was aborted due to big sum error.