move to raster buckets & tile parser handling raster decoding

src/renderer/raster_bucket.cpp

@@ -0,0 +1,14 @@
+#include <llmr/renderer/raster_bucket.hpp>
+#include <llmr/renderer/painter.hpp>
+
+using namespace llmr;
+
+RasterBucket::RasterBucket(const BucketDescription& bucket_desc) {
+}
+
+void RasterBucket::render(Painter& painter, const std::string& layer_name, const Tile::ID& id) {
+    // The painter renders rasters directly. This function is a no-op
+    // and exists just to satisfy the abstract superclass requirements.
+    // That way, we can avoid having raster buckets pass around
+    // references to tile data and/or rasters directly. 
+}