implementing new element 'eControllers' of type 'tController' for modelling controllers, e.g. interlockings

referencing on a controller element is possible via new attribute 'controllerRef' in new optional attribute group 'aOcpRef' that is attached to all controlled elements:

- switches and switchCrossings in 'tCommonSwitchAndCrossing'
- locallyControlledArea (where attribute 'ocpRef' is marked as DEPRECATED)
- levelCrossing
- signal (where attributes 'stationOcpRef' and 'signalBoxOcpRef' are marked as DEPRECATED)
- trainDetector
- trackCircuitBorder

closes #102

git-svn-id: https://svn.railml.org/trunk@396 997d4637-a740-4bf4-9a76-81fddc049f28