instead of using the old baseName=smack appendix=project.name approach,
we are now going convention over configuration and renaming the
subprojects directories to the proper name.
Having a prefix is actually very helpful, because the resulting
libraries will be named like the subproject. And a core-4.0.0-rc1.jar is
not as explicit about what it actually *is* as a
smack-core-4.0.0-rc1.jar.
SMACK-265
Also change StringUtils.escapeForXML() and Packet.toXML() to return
CharSequence instead of String. XmlStringBuilder now has 'optX' methods.
Remove XmlUtils in favor of XmlStringBuilder
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.
