SDK: Exclude backup files when creating a package
Refactor|libappfw: Root widget loads common textures

Added a virtual method that derived classes can extend.
libappfw|VRConfig: Keep projection matrix Z axis unflipped
SDK: Optional symbolic link deployment option
libgui|Debug|X11: Don't assert GL errors on X11

For some reason, on X11 we are seeing more OpenGL errors. It might be
due to the client/server nature of the window system; some operations
are attempted too early?
libgui|GLBuffer: Added "TexBounds0" vertex attribute

The texture bounds attribute is useful for example when rendering
geometry that uses a shared texture atlas; one can store the individual
texture bounds in the vertex data and use normalized (0,1) UV
coordinates, which a shader will then convert to coordinates on the
atlas. This also allows repeating UV patterns by applying wrapping in
the shader.