Polish generated POMs

- Include provided and optional dependencies
- Include information required for publication to Maven Central
Merge pull request #18 from wilkinsona/polish-generated-poms

* polish-generated-poms:
  Polish generated POMs
Streamline ehcache dependency and upgrade Spring Security

Depend upon ehcache-core rather than ehcache, thereby removing the need
for the exclusion of ehcache-terracotta.

Upgrade to Spring Security 3.2.3 (the 3.2.x line uses ehcache-core)