README indent
add release build type
share EHsc flag and allow redefinition of CL_CMD

this allow using the clang-cl front end by redefining CL_CMD
catch exception in video render method
sound check
loading shaders

Introduce reference types for shaders and programs. These only have
moving semantics as they represent a handle to a unique resource.

Note: vstudio 2013 does not support defaulting move constructors and
move assignment operators, so we have to put our own defaults there.
shaders require VAO and VBO in GL 3.2

Introduce resource objects for buffers and vertex arrays.

These objects are unique resource references, and only support moving
semantics.
blend scope allow activating blending
asynch loading of shaders from filesystem

Move fragment + vertex shaders into separate files.

Shaders are loaded asynchronously. The IO part is done in a background
thread, and - the shader definition done in a task of the display
thread.