adds cmake compilation

[blinard-BIOINFO]

@ksahlin

This PR introduces cmake compilation as an alternative to the makefile. It allows to build 2 targets:

• the StrobeMap binary (binary will be in /bin)
• a strobemer static library (built in /lib)

For the latter, it makes sure that the library is correctly recognized as a cmake-compatible library, e.g. the library can be found and linked by any CMakeList.txt after adding these lines :

FetchContent_Declare(
        strobemer
        GIT_REPOSITORY https://github.com/ksahlin/strobemers.git
        GIT_TAG        b1f2402f14773e1a93f1cda10555cbc3f7142764
        SOURCE_SUBDIR  strobemers_cpp
        OVERRIDE_FIND_PACKAGE
)
FetchContent_MakeAvailable(strobemer)
find_package(strobemer 0.1 REQUIRED)

Among other advantages, this just made it much easier for us to load and link the library in our CLion projects.

[ksahlin]

Great, thanks!