add GL.Program variant to load shaders from URLs (reloaded at compile time)
add a GL geometry class for points, rendered as two quads
add GL geometry builder for points, built as two quads w/UV coords at corners
remove extraneous style test
add support for multiple GL programs
geometry is grouped by program, max of one draw call per program per tile
NOTE: for initial testing, 'standard' shader continues to be baked into library, but new shader for rendering points is loaded by URL - will standardize
cache vertex attribute info in GL program layer
automatically calculate some of the vertex layout (stride, offsets, etc.)
commenting out attrib info we don't need right now
allow GLSL #defines to be specified at GL program creation time
add support for global GLSL #defines that apply to all programs
specific programs can override global properties by re-defining them
fix GLSL #define injections for non-boolean values (was wrapping values in parens, which is not allowed)
in shaders, move tile_scale from a uniform to a compile-time #define
commenting out point builder
some line/tile intersections are returned as points, which causes unexpected behavior when they then get built/rendered as points rather than lines
possibly constrain the applicable builders by layer, e.g. for roads, only allow line geoms