Since we're now back on using a central location for storing temporary
transfer files, it does make sense again to check for that location to
exist on service startup (refers to #16).

This reverts commit 10640754.

Refers to #16

The name reflects the functionality much better.

Since this is not a common (central) location any more, it doesn't make
sense to check for it during startup or similar situations.

Refers to #36

Refers to #36

Refers to #36

Refers to #36

Refers to #36

Refers to #36

Refers to #36

On an integer overflow while being in low-load state the probation
counter should not be reset to zero (indicating the load limit was
violated) but rather to the lowest value representing a valid load
(being _probation + 1).

Refers to #36

Refers to #36

Refers to #36

Refers to #36

Refers to #36

Refers to #36

Placed in namespace ATxCommon.Monitoring, using its own timer to update
the values.

Refers to #36

This way an email will be sent to an admin if configured so they have a
chance to check what's going on.

Megabytes have shown to be a bit clumsy in the configuration files, so
simply switch to the more useful Gigabytes unit.

Fixes #39

Refers to #36

Refers to #25

Refers to #24

Allow setting the log level explicitly from "Warn", "Info", "Debug" or
"Trace" in the configuration.

Default is "Info", fallback for invalid settings is "Debug".

Fixes #34

They were accidentially removed in commit cf183560 believing they had been
correctly moved by Visual Studio when refactoring the code and just forgotten
in the directory hierarchy. Who could guess Windows is so ignorant when
resolving paths?

Note that they are not included in the example configuration files as
these settings can easily mess up everything and should only be adjusted
with great care.

The default settings are valid on Windows 7 and Server 2012 and were
successfully tested on those versions.

Fixes #11

If a new directory is found in incoming but the move operation to
processing failed for some reason, the timestamp and username
directories (and potentially some partially moved data?) would remain
in processing. To prevent confusion about those "incomplete" transfer
candidates they are moved to the "ERROR" location.