Pushed new branch T26170-integration-of-rest-module.

My CppRestSdk and CppRestSdkQt modules are now integrated. I also added a doxygen file as a guide for how to use the module but I'm not sure whether this is displayed correctly, so this needs to be checked. In the end it should be on the doxygen page in the section Module Manuals (e.g. as Chart documentation).
If this is checked, the branch can be integrated in the master.

Pushed new branch T26170-Fixes.

• Linked manual in module manuals
• Cleaned up dependencies to cpprestsdk
• Removed/replaced MITK_USE_CppRestSdk by MITK_USE_cpprestsdk
• Removed global definition _WIN32_WINNT=0x0501
• Globally disabled C4251 warning

• The modules cannot be auto-loaded on Windows because the bin path of OpenSSL isn't specified.

• Replaced L"..." with _XPLATSTR("...") as string_t doesn't resolve to std::wstring on Linux.

• web::json::value is not comparable to NULL, use is_null() member function instead

• Removed unused variables and parameters