frontend: more verbose error
build: require datapack

To packing shaders into transition plugins.
build: transition -Wall
daemon: remove default value

need to include file from c.
graphics: move shader loading into daemon
graphics: adding fsquad helper
graphics: support default renderer (using fsquad)
fade: use new helpers
vfade: use new helpers
spin: fix render callback
transitions: provide a default implementation

The common case is to perform all work in the fragment shader.
Merge branch 'shader_helper'