add configure script
adapt zabr classes to new design
revert change in Makefile
avoid c++11
Merge branch 'svi'
add ZABR model (Andreasen, Huge: ZABR - Expansions for the masses, 2011)
Merge branch 'zabr2'

Conflicts:
	QuantLib/ql/experimental/volatility/Makefile.am
	QuantLib/ql/experimental/volatility/zabr.hpp
	QuantLib/ql/experimental/volatility/zabrsmilesection.hpp
add test case
Merge branch 'zabr2'