The previous implementation using the mutex had two issues:

1. The mutex was locked in a different thread than unlocked (DeviceModule constructor vs. handleException() thread). This results in undefined behaviour.
2. The boost::shared_mutex::lock_shared() function is not an interruption point, so applications did not terminate while waiting for initial values. (boost::latch::wait() is an interruption point.)

Just use enableDebugDataLoss() to enable debug output.

This will print always a lot of information if one or more devices is unavailable at server start. There is a high risk that these messages distract from the actual issue (broken hardware), hence it is better to remove this.

The message of this exception is usually lost and the user is left with
an obscure error about not calling shutdown() in the constructor without
any clue what was wrong with the config

- Have to use float because it that's what is descibed in the map file.
  We are skipping the lmap which would adapt firmware types to the application type, so the type has to match
  The type has changed because it was always wrongly set to double for all floating types data, although the catalogue suggests float. This fix requires the test to be adapted.

- testCircularDependencyFaultyFlags now uses modern AC without defining CS module and overriding defineConnections()

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The new order has the following advantages:
- values 0=OK and 1=Fault are compatible with frequent use of booleans like "is_error"
- values are matching ("accidentally") the DOOCS convention

modernise StatusMonitor interface

add convenient way to create constant PVs for use in generic modules

Killenb/7834 circular dependency faulty flags

Circular dependency detection: Outputs which are pogrammatically set to faulty are treated like external inputs.