Modernize cmake

[chipot]

This PR indents to fix a few issues I encountered when integrating mFAST in my own projects. Mainly the fact that find_package(mFAST) will modify CMAKE_CXX_FLAGS and CMAKE_CXX_STANDARD. This was a bit intrusive, and now the targets are setup to carry their usage requirements without touching global CMake config.

In the process I did a few other modifications:

• CXX_VISIBILITY_PRESET is set to hidden for all targets (matters for LTO performance)
• VISIBILITY_INLINES_HIDDEN is ON for the same reason
• install rule for headers are using FILE_SET HEADERS, removing the need to make an install(FILES) rules for them
• hand written code is replaced by built-in alternative when possible (for mFASTConfig.cmake.in and mFASTConfigVersion.cmake.in)
• make the file(GLOB) used for the source to be refreshed on build with CONFIGURE_DEPENDS

Resolves #122