[ENHANCEMENT] Parse GLSLangValidator version output in ToolChain

[thargy]

Running GlslangValidator -v produces an output similar to this:

Glslang Version: Overload400-PrecQual.1817 08-Feb-2017
ESSL Version: OpenGL ES GLSL 3.00 glslang LunarG Khronos.Overload400-PrecQual.1817 08-Feb-2017
GLSL Version: 4.20 glslang LunarG Khronos.Overload400-PrecQual.1817 08-Feb-2017
SPIR-V Version 0x00010000, Revision 8
GLSL.std.450 Version 100, Revision 1
Khronos Tool ID 8
GL_KHR_vulkan_glsl version 100
ARB_GL_gl_spirv version 100

When multiple versions of GlslangValidator are found on the same system (local directory, path, Vulkan SDK, etc.) it would be nice to pick the latest automatically by picking the latest version (by parsing this output). For bonus points, we can see which version of each spec. is supported.

[thargy]

An alternative/better approach is suggested in #94, however, if we maintain a fallback this would still be useful (the value of such a fallback if #94 is implemented is debatable, unless we compare the version of the exe to the wrapped library and find it is newer and so use in preference).