Misc. GPU improvements

hercules_cg/src/gpu.rs

hercules_cg/src/rt.rs

hercules_ir/src/ir.rs

hercules_opt/src/editor.rs

hercules_opt/src/fork_transforms.rs

hercules_opt/src/outline.rs

hercules_opt/src/utils.rs

juno_samples/dot/src/cpu.sch

juno_samples/edge_detection/src/cpu.sch

juno_samples/edge_detection/src/edge_detection.jn

juno_samples/edge_detection/src/gpu.sch

juno_samples/edge_detection/src/lib.rs

juno_scheduler/src/pm.rs