Previously, the default classpath was empty. Now, in the absence of the
user providing a classpath via the -cp option, the default classpath
will be ".". If the user does specify a classpath, the classpath that's
used will be exactly what they have specified, i.e. "." will no longer
be on the classpath unless specified by the user.

The app sample integration test has been updated to verify that "." is
only the classpath by default.

Fixes #115

Fixes gh-139

ServerProperties formerly had an @OnMissingBeanCondition
that didn't restrict the hierarchy. It also asserts that
the current context (not including parents) contains such
a bean. This led to an inevitable failure when there was
an existing instance in the parent context.

Fixed by a) searching only the current context, b) not
adding a ServerProperties bean if the context is not a
web app.

This information should probably be also available from the console and log similar to AutoConfigurationReport.

The JreProxySelector is used it to adjust the repositories
as they are added to the GrapeEngine. It looks at standard
System proeprties like http.proxyHost and http.proxyPort
and in addition consults standard JRE Authenticator features
for credentials (falling back to System properties
http.proxyUser and http.proxyPassword).

Fixes gh-136

Example:

    @RunWith(SpringJUnit4ClassRunner.class)
    @SpringApplicationConfiguration(classes = SampleDataJpaApplication.class)
    public class CityRepositoryIntegrationTests {

    	@Autowired
    	CityRepository repository;

Fixes gh-66.

Aether apparently doesn't use the java.net.* APIs for
TCP connections so it doesn't notice when a user sets
-Dhttp.Proxy*. To fix it is painful, and leads me to
suspect that actually we might want to parse a
settings.xml at some point (however unpalatable that
is).

For now I have added a Proxy to all RemoteRepository
instances that we create in the CLI if the user
has set -Dhttp.proxyHost (and/or -Dhttps.proxyHost for
a secure repository).

TODO: authentication. Is there a standard way to specify
that globally via system properties.

TODO: maybe use per-repository settings if provided
(e.g. in settings.xml).

Previously all EventListeners were eagerly instantiated
but that can cause problems because it happens quite early
in the lifecycle. Better to be explicit about the
supported types.