Project stucture changed to avoid symbolic links

The pom.xml file was changed. The packaging was changed to war instead of jar and the `web` folder was renamed to `webapp` and moved into `src/main/`.
In addition to this `disableClassMetaData`, `disableCastChecking` and `enableClosureCompiler` were set to `true`.

To compile the `GWT` project:  `mvn clean package`.

The compiled files can be found in `target/javaraytracerdemo-1.0-SNAPSHOT/`.