Upgrade central CMake in response to [Issue #106](https://github.com/MxUI/MUI/issues/106) and more

[Wendi-L]

Upgrade central CMake in response to Issue #106

• Remove MPI requirement in central CMake
• Remove MUI LIBRARY DESTINATION in header-only core code
• Remove *.f90 install for non-fortran in central CMake
• Change generic naming, i.e. rename src/config.h -> src/mui_config.h and rename wrappers/Python/mui4py/types.py -> mui_types.py
• Facilitate HAVE_MUI_DETECTED and MUI_VERSION define in central CMake

More updates:

• Update Python wrapper CMake to enhance automation on Python environment and packages detection
• Move Python wrapper building install & *.so generation into CMAKE_INSTALL_PREFIX and adding mui_setup.sh for linking
• Reorganised git ignore for improved readability and maintainability