Use files function instead of constructing path with meson.current_source_dir()

NOTE: This commit only tested on Linux (Ubuntu 18.04). Windows
build may not work as expected.

* Use meson >= 0.47.0 cause we use install_man function
* Add three helper Python script:
  * CopyFile.py: To copy file
  * CreateSymlink.py: To make symlink (both Windows and Unix)
  * GetZstdLibraryVersion.py: Parse lib/zstd.h to get zstd version
  These help emulating equivalent functions in CMake and Makefile.
* Use subdir from meson to split meson.build
  * Add contrib build
  * Fix other build
* Add new build options
  * build_programs: Enable programs build
  * build_contrib: Enable contrib build
  * build_tests: Enable tests build
  * use_static_runtime: Link to static run-time libraries on MSVC
  * zlib_support: Enable zlib support
  * lzma_support: Enable lzma support