Currently does not get the modules in a way that they can be downcasted
to test if StatusMonitor, etc

Correctly navigate to parent module via virtual path.

If someone includes the Logger into an ApplcationModule and calls writeAll() the Logger variable message will be written. To catch that cases set message empty after calling sendMessage and ignore empty messages in the LoggingModule.

    - Basic structure of test application
    - Added modules
    - Refactoring of StatusMonitor to provide a non-templated base class
    - Needs follow-up, for status see issue #14 and the linked follow-up
      ticket

- ConfigReader is in ApplicationCore.h, but was including ApplicationCore.h itself
- Added include guards to ApplicationCore.h, although it's not stricktly needed (all included headers have one). Might speed up complilation because it makes it easier for the parser.

Connecting a device only works if the PVs are readonly! So one has to
use the logical name mapping backend. This also allows to select only a
subset of the device PV to be added to the history module.

I observed that, after reading the message sometimes the log level was
wrong. Most likely because it was updated after the message was read.
Now the log level is bound to the message. This also reduces the number
ctk variables.

Fix missing object name in the example.