add check for native fixings
add cms spread coupon
add inspector for underlying
add cms spread coupon
add swap spread index
add cms spread coupon pricer
add coupon that strips cap and floors from existing coupons
add files
make member name accessible by implementations
Merge branch 'cmsspread'

Conflicts:
	QuantLib/ql/experimental/coupons/lognormalcmsspreadpricer.hpp
	QuantLib/ql/experimental/coupons/strippedcapflooredcoupon.hpp
	QuantLib/ql/experimental/coupons/swapspreadindex.hpp