* Improve usability of root-config.bat

Handle unknown feature and/or option, addressing the issue #7662 on Windows. Gives something like:
```
C:\Users\sftnight>root-config --flags
--flags: Unknown option or argument!

Usage: root-config [options]

  --arch                Print the architecture (compiler/OS)
  --platform            Print the platform (OS)
  --libs                Print regular ROOT libraries
  --glibs               Print regular + GUI ROOT libraries
  --evelibs             Print regular + GUI + Eve libraries
  --cflags              Print compiler flags and header path
  --bindir              Print the executable directory
  --libdir              Print the library directory
  --incdir              Print the header directory
  --etcdir              Print the configuration directory
  --tutdir              Print the tutorials directory
  --srcdir              Print the top of the original source directory
  --auxlibs             Print auxiliary libraries
  --config              Print arguments used for configuration with CMake
  --features            Print list of all supported features
  --has-<feature>       Test if <feature> is compiled in
  --version             Print the ROOT version
  --git-revision        Print the ROOT git revision number
  --python-version      Print the Python version used by ROOT
  --python2-version     Print the Python2 version used by PyROOT
  --python3-version     Print the Python3 version used by PyROOT
  --ncpu                Print number of available (hyperthreaded) cores
  --cc                  Print alternative C compiler specified when ROOT was built
  --cxx                 Print alternative C++ compiler specified when ROOT was built
  --f77                 Print alternative Fortran compiler specified when ROOT was built
  --ld                  Print alternative Linker specified when ROOT was built
  --help                Print this message

C:\Users\sftnight>root-config --has-feet
 --has-feet: unknown feature!

C:\Users\sftnight>root-config --has-feet --has-pyroot
 --has-feet: unknown feature! yes
```

* Set the return code to 1 if anything fails