This is needed to add all device variables to e.g. the history module.

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.

If the hdf5 library is not available, the MicroDAQ module is automatically not build. You don't have to specify -DBUILD_MICRODAQ=OFF to make cmake run through.

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.

It allows you to check how the controller behaves and to monitor the changes in doocs histories, for instance.

solves #70

- worked around gcc bug buy adding a useless default constructor
- removed dangerous convenience referene which would be broken by copy constructor and assignment operator

Merge VirtualModules which have the same name. This doesn't really make a difference, but e.g. the output of dump() will be much cleaner.

Fixes #68