All outputs of any kind of duration should be using a human readable
variant of the time span.

Fixes #25

Since they only depend on current configuration settings they should as
well be accessible through the config class. This way they can be used
in a consistent fashion across different projects.

Fixes #24

With proper logging in place this is now easily doable, therefore we
don't need the "ValidationWarnings" workaround any more.

Refers to #3

Currently this is almost entirely untested and configuration for email
notifications is yet to be done.

Refers to #3

Since we have more to share between the applications than just the XML
wrappers, this is the location to keep common classes and methods.

Note that this only adds the new class library, it does not yet adjust
the existing service code to use it!

Refers to #21

An email will be sent only if the time since the last one exceeds the
new configuration option "GraceNotificationDelta", defaulting to 12
hours.

Fixes #1

This is NOT YET reflected in the configuration example XML!

Using an optional element in the configuration XML, defaulting to "true"
via the configuration class constructor.

Refers to #16

The method checks folders in the grace location for their age (parsing
the folder name timestamp) and generates a report for those older than
the given GracePeriod.

This is related to issue #1