* 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