Make installable

[kou]

• Add support for pkg-config
• Add support for find_package(FastPFOR) in CMakeLists.txt
• Add support for installing header files
• Add support for installing static library
• Add support for linking static library from shared library (-fPIC is needed for build option)
• Use "FastPFOR" not "FastPFor" for project name

Note that we need to bump "PROJECT_VERSION" in CMakeLists.txt when we release a new version. "PROJECT_VERSION" is used in fastpfor.pc and FastPFORConfig.cmake to provide version information.

[kou]

Use "FastPFOR" not "FastPFor" for project name

It seems that you want to use "FastPFOR" instead of "FastPFor". So I do this. It it's wrong, I'll revert the change.

[lemire]

This is very good work.

I verified that this seems to do the right things!