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
* added amit functions in readers
* cacheHasChanged functions (needed because data of caches are loaded in background)
* pinned small caches
* CDatabaseReader::readInBackgroundThread uses admitCaches now
(applied after 1st performance fix for cache was ready)
* utility functions to detect if only caches are used
* renamed some functions
* renamed some db flags and added new ones
* 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
