Rational: Normally calling synchronize multiple times does not matter. However, it can time out if the cache is in use (e.g. saving) and create an exception. This exception is just unwanted "noise".
* multi format compatible (automatically detect format)
* flag if cache values shall be overridden
* init from resource files (those are the files coming with the installer)
* automatically read in background if reader is (already) in its own thread (otherwise cache.set() ASSERT)
* added getAirlineIcaoCodeForUniqueDesignatorOrDefault and getAirlineIcaoCodeForUniqueIataCodeOrDefault from reader/web data services
* rearranged order of functions in ICAO reader
* added some more functions like "containsXX" in reader
* in case the internet provider is down, this is not detected
* extended test to detect if access is possible
* in case of downtime this indicated in status component
* use doWorkCheck
* relaxed doWorkCheck in unit tests
* removed isShuttingDown, gracefulShutdown
* set timer object name (in case something is wrong, we might see the name in the log)
* now ignore incomplete entities for airline/aircraft ICAOs from DB
* utility functions to find invalid designators
* adjusted unit test, avoid taking a random element
* and fixed 4 wrong ICAO entries in DB
* new read state "skipped"
* renamed to "isNetworkConnectedAndAccessible"
* checking before reading, which would only fail if network is not accessible
* added amit functions in readers
* cacheHasChanged functions (needed because data of caches are loaded in background)
* pinned small caches
* CDatabaseReader::readInBackgroundThread uses admitCaches now
* view already filter incomplete data
* as result, info object count values are aligned with data eventually parsed (which will allow to detect changes by comparing counts)
* smaller adjustments to allow airlines with designator
* adjustments to use deferred caches
* removed simulator from CAircraftModelSetLoader`s signature as it was not used
* only change current simulator when explicitly set (avoid unintended setting)
* added function to obtain number of elements from model caches
