Maven plugin groupId filtering should be exact (#649)

Following from the work in #649, I used the plugin to filter "org.springframework" groupId artifacts. Noted that (for me anyway) an unexpected side effect was the removal of "org.springframework.boot" artifacts. Would it be less surprising to require an exact match on groupId?

This is also mentioned in a long standing JIRA on the Maven Dependency Plugin project: http://jira.codehaus.org/browse/MDEP-237