Add BOSH subproject (SMACK-187)
Cleanup of build.gradle

- Moved helper code at the end
- Add description to the POM
Raise jbosh version to 0.7.0
Substitute MXParser with a call to XmlPullParserFactory

This makes Smack more portable, as there are platforms that support the
XmlPullParser interface, but not MXParser (e.g. Android).

Also enable checkstyle check that MXParser is not used.
Remove the dependency on javax.xml.transform

Not all platforms support this API (e.g. Android). Strip the
prettyPrint() method since it wasn't used anyway.

Also move XmlUtil in a more appropriate package.
SMACK-53: create Version.Provider and .Manager

The Version.Provider is used to parse Version IQs. Integration:

	providerManager.addIQProvider("query", Version.NAMESPACE, new Version.Provider());

The Version.Manager is used to reply to Version IQs. Integration:

	Version.Manger.getInstanceFor(connection).setVersion(
		new Version("App Name", "1.23", "Operating System"));
SMACK-53: reviewer feedback updates

 * corrected extensions.provider
 * using weak connection reference in manager
 * license update
 * removed old namespace ELEMENT string
SMACK-53: remove flood protection
refactor Version.Manager and .Provider into own classes

This patch does:
 * refactor the Manager and Provider into separate classes in the
   hierarchy, comparable to iqprivate
 * update extensions.provider
 * rework how START_TAG parsing is done
 * re-use of the NAMESPACE element
 * removal of flood protection
 * weak-reference connection class
 * improve packet filter in the manager
 * add a test case