MatrixKit: Make internal Swift code usable from Objective-C

**Create separate projects for MatrixKit library and MatrixKit code sample**

It will allow to decouple sample code from MatrixKit code and use specific project configurations for each projects.
And it will be an opportunity to have a target named `MatrixKit` that will allow to use Swift code in Objective-C easily without renaming `Product Module Name` build setting of current `MatrixKitSample` target.
Indeed in order to use Swift code in Objective-C inside MatrixKit framework we need to import `-Swift.h` in Objective-C implementation files (.m). As Product Module Name is currently `MatrixKitSample` in MatrixKit project and generated pod project has `MatrixKit` as Product Module Name it could not compile for both cases without renaming the Product Module Name.

Start by examining the MatrixKitSample target, the proposed separate MatrixKit and sample projects, and the generated pod project’s Product Module Name setting. Done means the library and sample use separate project configurations and Objective-C implementation files can import the generated Swift header under both the local and pod-generated MatrixKit configurations.

Written by the indexing model from the issue text.