This prevents at least the log file from being cluttered up completely
in "normal" operation. As stated in #50 the level for those messages
should be configurable to allow for easy adjustments without the need to
recompile the service itself.

Otherwise AutoTx will try to process them in each iteration but fail
right away, thus blocking all other transfers while the dir is there.

Fixes #49

Fixes #38

In addition to the previously added package name / path, the marker file
now gets populated with the following:

- host name (redundant, but easy to parse from here)
- the time stamp when the update happened
- build commit
- build configuration

The encoding of the file is changed to be ASCII, otherwise PowerShell always
places the ugly BOM (byte-order-mark) at the beginning, confusing a lot of
editors.

Fixes #46

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

Fixes #44 (hopefully!)

Fixes #43

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 #5

Refers to #40

Fixes to #5

Refers to #5

Refers to #40

Report if the service account is not a member of the local group
"Performance Monitor Users" when the service binaries are being updated.

Refers to #40

Membership in the group "Performance Monitor Users" is required for the
CPU load monitoring to work, so add the service account to this group.

Refers to #40

Fixes #5

Refers to #5