Move the build system to Tycho

The current build system uses an ad-hoc unstable and non-standard setup that makes Maven call the PDE headless build process.

Lately, the problem of building Eclipse plugin with Maven has been addressed by the Eclipse community and the result is Project Tycho (http://www.eclipse.org/tycho/) which makes easier to build Eclipse plugins on the command line using maven.

The idea is to replace the current build system with Tycho so that we can control and integrate the build process better.