All combinations of tradeoff-exploration-exploitation run through with SeqDesign. Reverted BayesInf to the current develop branch

Merge branch 'fix/sequentialdesign' of https://git.iws.uni-stuttgart.de/inversemodeling/bayesvalidrox into fix/sequentialdesign

Merge branch 'fix/sequentialdesign' of https://git.iws.uni-stuttgart.de/inversemodeling/bayesvalidrox into fix/sequentialdesign

example_analytical_function_testSequential runs through all the sequential options and contains notes on which do not work.
Choose_next sample now uses only one set of candidate samples

Merge branch 'develop' of https://git.iws.uni-stuttgart.de/inversemodeling/bayesvalidrox into develop

Two tests for the ExpDesign became unneded due to change in the input parameters of ExpDesigns.generate_ED()

A first draft of the contribution guidelines can now be found in `CONTRIBUTING.md`.
The website was rebuilt, but does not include the guidelines yet.

User guide startet for models, surrogate training, sequential training, postprocessing and BAyesian classes. The guide now contains simplified UMLs (for BayesInf not yet done).

Webpage includes quickstart, user guide, tutorial, example collection and api.
One new example was added for the user guide.

Build api pages with autosummary and modified templates to include class documentation.
Tutorial updated to BVR 1.0.0 (engine use).