Tidied up build.

Disabled aggregation of "doc" task in "root" project, removing previous
fudge (giving "doc" no files to work with in the "macros" and "core"
projects). Also removed another hack (empty artifact repository) that
was no longer required.
Removed redundant Maven & style files.
Used simpler timestamp method for timestamping build.
Replaced org.joda.time classes with new Java 8 java.time classes.

Relocated org.facsim.util package object from "Macros" sub-project to
"Core" sub-project. Also added project start date to build.
Added class to implement Behavior trait using Manifest data.
Merge remote-tracking branch 'origin/master'