Add a flag to add suppress messages to the top of every file by default

`--closure_suppressAll`

Unless we find a top-level comment with an annotation like `@closure`

Alternatively we could just use, and unset `ADVANCED_OPTIMIZATIONS`

```
###
// ==ClosureCompiler==
// @compilation_level ADVANCED_OPTIMIZATIONS
// ==/ClosureCompiler==
###
```
