Merge pull request #23 from igitur/enable_QL_NEGATIVE_RATES

Enable QL_NEGATIVE_RATES
Merge branch 'Ver-1.4' of https://github.com/amaggiulli/qlnet
Merge pull request #18 from igitur/calculate_notionals_in_cpibond_constructor

Calculate notionals in cpibond constructor
Merge branch 'Ver-1.4' of https://github.com/amaggiulli/qlnet