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

- removed sleep
- put reading to end of loop (process initial value before blocking)

It is suffiecient to have the message being push type.
readAny of the ReadAnyGroup will update poll type variable
automatical once there was an update of the push type message.

Some custom tags from private servers have been removed.
Added "CS" tag, which allows to use findTag on the Logging module
and connect it directly to the control system.

the swicth because order is not important for these.

ModuleList serves as a container for VariableGroups. The VariableGroups
mirror xml modules in the config file.

Unfortunatly this currently breaks the ServerHistory module, as it relies on slashes in accessor names. The MicroDAQ module had the same issue but has already been fixed. This fix can be adopted to the ServerHistory module as well.

Now one can add ScalarOutput and ArrayOutput variables to the history modules by using tags.

This is still not nice. Now for every data type an individual module needs to be created.

Do not rely on EntityOwner for accessig Application object.

- renamed timeout to period.
- introduced PeriodicTrigger::sendTrigger
- mainloop logic bypassed on startup if owner application is in testable
  mode.

- Timeout is now in milliseconds to allow more flexibility
- Default timout can be specified in the constructor
- Make sure the time interval is perfectly matched by using sleep_until instead of sleep_for