One file ("config.common.xml") containing site-global configuration
settings, the other one (the file name equals the host name with a
".xml" suffix) containing host-specific settings.

Both files use the same syntax and may contain the same setting
attributes with the host-specific one having priority over the
site-global one.

Refers to #18

They are already set by the XmlSerializer class to the default value of
the corresponding data type.

Do not serialize the status XML if the actual value of ServiceSuspended
and / or LimitReason has not really changed. This effectively prevent
the "heartbeat" value (LastStatusUpdate) from being updated once per
AutoTx timer cycle.

Closes #19

Refers to #26

Having the total progress is much more useful than for the individual
files, especially for transfers with many files.

Closes #26

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