Put all translations into the namespace QDoc and fix warnings
about invalid tr()-usage by removing the free tr()-function
from tr.h. Provide QCoreApplication::translate() for bootstrap
builds.

Change-Id: I2b6931188346f290e80e14b84adff8892d8a860f
Reviewed-by: Martin Smith <martin.smith@digia.com>
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>