Fixes#306 - Merge jetty-parent into jetty-project.
- Removed jetty.parent dependency, moving all relevant sections to
jetty.project's pom.xml.
- Introduced profiles for JDK 8 only modules and configuration, and
for JDK 9 only modules and configurations.
- Major cleanup of pom.xml files.
- All Maven Plugin now declared in alphabetical order in
pluginManagement section of jetty.project's pom.xml.
Simone Bordet
Jesse McConnell