Clean up project structure

Split the monolithic `stirling` project into three subprojects:

- `stirling-core`
- `stirling-fix-console`
- `stirling-fix-perftest`

While at it, rename the FIX console to `fix-console.jar`, use `sbt-start-script` for the FIX performance test, and remove IDE cruft for Eclipse and IntelliJ IDEA.