Provide more systematic support for primitives in C(++)

[kruegers]

Some(tm) cryptographers prefer to implement cryptographic schemes in C(++). Extend the integration interface of #13 such that algorithms implemented in C(++) can be integrated as well. In particular, add a question about the respective programming language. If C(++) is selected, generate stubs for an JNI after the algorithm type is selected. Depending on the algorithm type, different methods need to be generated (e.g. ciphers need at least the methods encrypt, decrypt, generateKey). Finally, ask the primitive developer to connect methods in the JNI with the ones in their C(++) implementation.