Separation of Core- and domain specific parts

[soen]

What kind of change does this PR introduce? (Bug fix, feature, docs update, ...) A restructure of the Conjunction codebase seperating the Sitecore specific parts from the pure Core parts.

What is the current behavior? (You can also link to an open issue here) See issue #26 for more information.

What is the new behavior (if this is a feature change)? The core assembly is split into two separate assemblies:

• Conjunction.Core
• Conjunction.Sitecore

whereas the Conjunction.Core assembly only contains abstract interfaces and generic implementation details. Likewise, the assembly named Conjunction.Sitecore contains all the concrete implementation details in the context of using Sitecore - this assembly is dependant on the Conjunction.Core assembly.

Does this PR introduce a breaking change? Yes, comsumers of the API will have to include both the Conjunction.Core and Conjunction.Sitecore assemblies, instead of just Conjunction.Foundation.Core.

Please check if the PR fulfills these requirements

• [x] The commit follows our guidelines: https://github.com/soen/Conjunction/blob/master/CONTRIBUTING.md
• [x] Tests for the changes have been added (for bug fixes / features)
• [ ] Docs have been added / updated (for bug fixes / features)

Other information: The docs will be updated in a later PR, which address updating docs in general for vNext.