Bundle update snapshots

This pull request add support for new command.

See https://issues.apache.org/jira/browse/KARAF-2186

bunde:scanner (new command)

```
@Command( //
scope = "bundle", //
name = "scanner", //
description = "Scans and updates snapshot bundles.", //
detailedDescription = "Scans installed snapshot bundles, updates them from remote maven repository, and re-deploys changed jars in karaf.")
```
Depends on
https://issues.apache.org/jira/browse/KARAF-2183
https://github.com/ops4j/org.ops4j.pax.url/pull/7

Was tested on karaf 3.0.0-SNAPSHOT