Recover CBS function

[jaromrax]

Recover CBS function from fitResult and integrate it in the full range. That way the full peak area could be obtained. Also there could be a way to relate nalpha and n parameters to fit-region limit to recover full peak area.

[jaromrax]

multi_cbs project solves that in one_cbs()
current fit should be somehow replaced/enhanced by more open version
of multi_cbs (from github)