Intern entity strings for table and column names.
Review Request #121255 - Created Nov. 26, 2014 and submitted
This should drastically cut down on the amount of allocations done
by the AkonadiServer. Currently, the getters will do the conversion
from QLatin1String to QString on every call. By reusing the data
via a function-local static const QString object, we can eliminate
all of these allocations and increase the cache locality as well.
Tests all pass, and KMail with a restarted Akonadi is still happy (no runtime errors that I can notice).
Perf shows that the string allocations are mostly gone now.