Move file related methods to FileUtils
Renamed DefaultRosterStore to DirectoryRosterStore
Make DirectoryRosterStore use elements for whitespace content

If whitespace (e.g. \n \t) needs to be preserved, then XML elements
should be used instead of attributes. Since we do this now in
DirectoryRosterStore, there is also no longer a need for an
specialized StringUtils.escapeForXML().

Also introduce XmlStringBuilder, which should become the default way
to implement Packet.toXML() and the like.
Always lookup DNS SRV RR on connect()
Use XmlStringBuilder in most toXML() bodies

Also change StringUtils.escapeForXML() and Packet.toXML() to return
CharSequence instead of String. XmlStringBuilder now has 'optX' methods.

Remove XmlUtils in favor of XmlStringBuilder
Streamline LastActivity API, add enable/disable

Allow LastActivity to be enabled/disabled. The API is now similar to the
ones of the other Managers. Added unit tests.
Fix Socks5BytestreamManager.determineProxies()

We need to catch XMPPErrorException and *NoResponseException* and
blacklist those entities.
Raise source compatibility to 1.7 (Java7)

Now that Java 8 is released, it's time to raise Smack's source
compatibility. Let's also use some of the "new" Java 7 features like
"catch multiple".