Issue#48, two new dependence function

[ahaselsteiner]

Implemented two new dependence functions, one function is called 'logistics4' and one function is called 'alpha3'. Changes on the architecture of viroconcom where necessary as the architecture was built to support only dependence functions with 3 parameters (see issue #48).

However, 'logistics4' has 4 parameters.

'alpha3' required even more changes as this function includes a logistics4 function. Thus, it has actually 7 parameters, but only 3 of the 7 seven parameters are fitted.

These functions were implemented to support the wind-wave model that was proposed in the publication 'Global hierarchical models for wind and wave contours'. The original implementation was in Matlab and is available here: https://github.com/ahaselsteiner/2020-paper-omae-hierarchical-models

[coveralls]

Pull Request Test Coverage Report for Build 381

• 90 of 90 (100.0%) changed or added relevant lines in 3 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+2.06%) to 89.228%

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Totals
Change from base Build 363:	2.06%
Covered Lines:	1052
Relevant Lines:	1179

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💛 - Coveralls

[ahaselsteiner]

After a brief discussion with @kawindme we decided to merge the pull request. We will make this a new release.