SLING-3120 - Allow installing/updating the install support bundle from
the servers view

- extract an OSGiClient into the api bundle so that it can be reused
- when connecting to a Launchpad server, read the version of the tooling
support bundle
- add UI support for installing/updating the bundle, but without
actually performing the operation, since bundle is not yet available
outside the eclipse-m2e-ui bundle.

git-svn-id: https://svn.apache.org/repos/asf/sling/branches/tooling-ide-vlt@1526474 13f79535-47bb-0310-9956-ffa450edef68