* 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
* removed from component cache
* kept renamed component caches as stubs for later usage
refs #646, removed gui state cache as it causes build issues on Jenkins
(idea was to keep the classes as stubs for later usage)
* removed iconForModel from interface and aircraft config parser
* CPixmap support for loading pixmap from file
* Access to model of model set loader by model string
* icon path as member of CAircraftModel
* use own default constructor error: default initialization of an object of const type 'const BlackMisc::CIcon' without a user-provided default constructor static const CIcon empty;
* same for CDbOwnModelsComponent()
* fixed guard
