Split search strings more intelligently.

QTextBoundaryFinder knows more ways to find a word break than just
looking for space characters.  Use it.
Add vCard() method to Person
Add a few clarifying comments.
Fix cached node handling in social network adapter

Previously, cached nodes were not pushed to the node stack correctly,
resulting in incorrect behaviour.  This commit also ensures that when
cached entries for a cached node are used as the model data, they are
filtered according to the current filter set, in case the filters have
changed since the cache entries were retrieved.
Merge pull request #104 from chriadam/socialcache

Fix cached node handling in social network adapter
Merge pull request #102 from martinjones/vcard

Add vCard() method to Person
Merge pull request #96 from adenexter/filters

Split search strings more intelligently.