GitLab

- moving the following classes over from OPAL to CLASSIC
  o OpalField       -> ClassicField
  o OpalRing        -> Ring
  o OpalRingSection -> RingSection
  o LossDataSink
- clean up
- splitting Options into classic and opal options

- remove 'using namespace' from header files
- remove 'using std::string' and 'using std::abs' from header files

For reason see:
o http://stackoverflow.com/questions/5849457/using-namespace-in-c-headers