Expand potential of TCS scripts

Having a realistic TCS simulated on board increases significantly the interest of simulated train driving. Nowadays in the world there is a wide variety of TCS. OR allows the implementation of specific TCS using scripting. The available features, while being quite powerful, are not complete. The aim is to increase the hooks within OR to allow further features to be implemented in the TCS scripts.
48 generic cab display controls, of which 32 may also be used as on/off commands, are introduced; they can be completely configured by the TCS script.
Further hooks to get data from the main OR code and to put data there are added, among them a hook to get the player locomotive handle, which enables the script to access the complete simulation environment.
Hooks to access data about all types of signals are added; this can be used to access signals for exclusive use of the script, e.g. to get points where the TCS starts or ends in a route.