find_package() now also stores the required version automatically, so it
can be used by FeatureSummary.cmake.
This was one of the requested features for setting up nightly builds
for KDE, since with this functionality it will be possible to write
a file at the end of each project which lists all required packages
and their versions. This file could then be compared for equality
with an older one and if something has changed the build maintainer
can be emailed.

In FeatureSummary.cmake there is now a new function feature_summary(),
which also allows to print the log to a file or into a variable.
It also allows to specify whether to append to a file or to write a new
one, and what information to log.

Docs are still missing.

Alex