Reiterate and refine examples (various_feature_maps and kernel)

[JanSchnabel]

• addresses Issue #11
• @FredericRapp please check the QGPR/QGPC examples
• add full use of sQUlearn to example_projected_kernel.ipynb. I guess we want this, @David-Kreplin

[David-Kreplin]

Sorry to ask, I can't simply remember how example_projected_kernel.ipynb looked before: what did you change? I think, I did also some cleaning of that file, because now there is a conflict. I can fix this, after I know, what you've changed.

[JanSchnabel]

Sorry to ask, I can't simply remember how example_projected_kernel.ipynb looked before: what did you change? I think, I did also some cleaning of that file, because now there is a conflict. I can fix this, after I know, what you've changed.

Basically, I used QSVC for solving the classification problem instead of sklearn SVC. However, I left the use of sklearn as comments.

[David-Kreplin]

Example is fixed