Linux Support

The biggest change in this version is the migration from Visual Studio solutions to CMake.

With this change, Raygun can now be built on Linux.
Small adjustments were made to the code in order to fully support Linux.

• Use different application icon colour depending on build type
• Fix uninitialised data arrays in profiler
• Fix Vulkan resources use-after-free bug on engine shutdown
• Improve handling of window resize events