Use maven-dependency-plugin for finding artifacts

This change introduces the maven dependency plugin in order to resolve project dependencies.
This seems to work despite the changes in the enforcer plugin in 1.3.1. It is an
experimental fix for issue #13. However there are a number of scenarios that still need
to be examined. I am concerned that this fix will break backwards compatibility with older
maven versions. So more testing is needed before I will be happy to merge this into the
master branch ( and do a release ).

The sample project has be updated to include this snapshot as a dependency (as well as
updating the enforcer plugin version to 1.3.1. As I have not released a snapshot as yet
you will need to run mvn clean install on the victims-enforcer project to test these
changes against the sample project.

A couple of other minor changes. The tests were polluting the users victims database. This
is not acceptable. The database has been moved to a temporary directory on the
file system and the http webservice has been mocked out (already was). I've also
introduced the convention of prepending debug output with [victims-enforcer]. This
makes it easier to grep for debug messages.  I will have to refactor the logging
to provide a more sane approach to doing this at some stage.

- Grant.
Fall back to old methods for collecting artifacts

If a failure condition exists or an API incompatibility we fall back
to other artifact collection mechanisms without failing completely.
This should hopefully improve backwards compatibility.
Added some much needed null pointer checks.
Add flexible usage options for CI jobs.

Added system property to overwrite pom.xml settings.
This should address concerns outlined in issue #18.

Usage example:
    mvn -Dvictims.skip.updates=true

Added 'weekly' updates option. Compares current date
and last update date to current year, and week of year.
This should address concerns outlined in issue #16.

Database synchronization issues will now not stop the
victims scan. If the synchronization operation fails we
print a warning message and try to continue the scan.
This should address the problem presented in issue #19.

All of these changes are experimental and require further testing.
There is an expected linkage failure for outdated version of the
enforcer plugin. In order to catch the linkage error we need to
use Throwable instead of Exception here as that also catches
Errors.
Bump victims-lib version.
Merge branch 'issue13_plugin_compat'

Conflicts:
	.gitignore (order of ignores different for .idea files).