Change eclipse update site and feature generation to use common maven mechanisms

Change the Eclipse update site generation:

1) make the Feature projects into maven projects, adding a pom specifying "jar" packaging, and making the jar have the normal LIC/NOT/DIS and the feature.properties and feature.xml files

2) make the update site into a maven projects, having its pom:

• invoke the feature poms to build those features
• use dependency:dependency-copy to copy plugin artifacts into its plugin directory
• use dependency:dependency-copy to copy the feature jar artifacts into its features directory
• use the ant-run plugin to build the update site