Pass manager fixes and example

Cargo.lock

Cargo.toml

juno_samples/multi_return/Cargo.toml

juno_samples/multi_return/build.rs

juno_samples/multi_return/src/cpu.sch

juno_samples/multi_return/src/gpu.sch

juno_samples/multi_return/src/main.rs

juno_samples/multi_return/src/multi_return.jn

juno_scheduler/src/pm.rs