Break out parent POM into separate module

To date, ModeShape's parent POM has been in the top-level directory of the codebase, and has served two purposes: define all of the inherited information (e.g., dependencies, dependencyManagement, properties, property-based profiles, repositories, plugins, etc.) and define the modules and profiles used for the complete build. They really are separate responsibilities, and should be broken up as such.

This is not an essential change, as the build certainly functions in its current form, and as the separation may be mostly cosmetic (although breaking the parent POM out without any of the build-related modules and profiles means less information is inherited). Thus, before this change is committed, we should evaluate whether it's really worth doing.

I welcome any thoughts and opinions as to whether this is a Maven 3 best practice.