Adding project metadata to pom.xml

Adding project metadata to pom.xml, including everything required for the Maven Central repository except for a ```developers``` section, which often requires some discussion among contributors.

See
http://central.sonatype.org/pages/requirements.html

A few other sections were added (```<pluginManagement>``` and ```<dependencyManagement>```) to reduce Maven warnings and make the scopes of dependencies explicit (notice that several of the dependencies originally listed are not required at any scope).