Create property to hold local maven repository location

In their current state, both build.xml and .build/build-resolver.xml refer to the local maven repository by "${user.home}/.m2/repository" in multiple places.
It would be nice instead to have a property store this location, and refer the property vs the actual location itself.
If one needs to change this maven repository location for their environmental purposes, this change makes it easy since it will need to be changed only at one place (the value of the property) vs changing all the direct references to the repository location.