* Created examples/ wgpu-example-compute-runner + wgpu-example-compute-shader.
* Working compute example, can compile and run, set local_size. Validated changes do not break rendering example.
* Added complete list of ExecutionMode's to be specified underneath ExecutionModel. Replaced SpirvAttribute::Entry ExecutionModel with an Entry struct, which includes a Vec of ExecutionMode, ExecutionModeExtra to be submitted in entry.rs. Compute example runs. Passes all tests.
* Changed Cargo license info for compute examples. Simplified compute runner to be more similar to other wgpu example. Split of entry logic in symbol.rs to separate function. Fixed issue in builder/mod.rs.
* Pulled in reorganization changes to crates + examples. In symbols.rs moved really_unsafe_ignore_bitcasts to its own Symbol match. In entry.rs, entry stubs now return the fn_id, so that entry_stub() can add the execution modes in one place. Passed all tests.
* cargo fmt
* Removed duplicate examples. Fixed cargo fmt bug in compute runner.
