Progress towards #448
Lots of warnings from g++7.2, these are addressed in #423 which hasn't been merged yet.
CMAKE can be cleaned up a bit - may put back in the ability to use older cmake and just throw errors as necessary,
otherwise just force people to use at least cmake 3.1
-Make CEREAL_THREAD_SAFE be 0 or 1 instead of present or not present
-Move CEREAL_NOEXCEPT to macros.hpp
-instead of individual locks, can now use StaticObject::lock() to request a lock if CEREAL_THREAD_SAFE is enabled. If
not enabled, this call returns an empty object. The lock returned acts just like std::lock_guard, but uses
std::unique_lock internally
-Made a bunch of requests to StaticObject::getInstance const
-Added first stab at multithreaded tests with versioning and polymorphism
- add install target to install config-module for
which creates an INTERFACE library
- add unittest to test config-module
- add option to skip tests and install only
- fix MSVC compatibility problem in CMakeLists.txt
