Visual Studio 2017 defines the VS150COMNTOOLS env variable which
kdevelop-msvc.bat ignored till now. By default VS does not set the
VS150COMNTOOLS as system-wide variable so we have to do be a bit more
clever to detect the VS2017 install.
Also allow to start using VS2017 compiler, using either 32 bit or 64 bit
compilers by prompting the user.