Fixes #47

If users don't have the permissions to scan a folder hierarchy, they're
not supposed to transfer it anyway - so just show an error message.

Fixes #48

Fixes #44 (hopefully!)

Fixes #43

Refers to #5

With this commit all required changes for having the configuration in
two separate files should be completed.

Fixes #18

Refers to #2

Refers to #2

We can just derive a status change from the fact that the file system
watcher has fired, so no need to evaluate all kinds of things first.

Refers to #23

Refers to #2

Refers to #2

Refers to #2

Refers to #23

Refers to #2

Refers to #2

Sometimes the TaskDialog doesn't work but raises an exception. Until we
can reproduce and fix this issue we simply provide a fallback using the
(less user-friendly) MessageBox.

Refers to #2

This is the last missing strict requirement for the first version of a
tray app, so this commit closes #2.

Let the user pick a directory, check size and let the user confirm and
eventually submit it into the incoming directory after some sanity
checks.

Refers to #2

Refers to #2

Refers to #2

Refers to #2

Refers to #2, #3

Refers to #2

Refers to #2

Refers to #2, #26

NOTE: currently any update to the progress bar will also re-display the
balloon tooltip. These two things should be separated!

Refers to #2

Refers to #2

All projects (and namespaces) should start with an "ATx" prefix, having
a capital "AT" and a lowercase "x".

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

Refers to #3

Refers to #2

Refers to #2

Refers to #2

Refers to #2