Added json cofiguration feature for Train Track system

[cambrialas]

This feature add configuration for connection points in the train track system.

The json file, can specify connection points for any part type.

For each part type, an arbitrary number of connection points can be specified.

Each connection point consist of a position and direction, and a group of related pieces, which can be connected to this connection point.

Related pieces groups, is specified with a name and a list of parts names.

Related pieces group can be related to a connection point by related pieces group name

The json file is read at startup and the related pieceinfos is updated accordingly.

The json file, now configures the 9 Volt and 12 Volt train track sections, as an example, can easily be expanded.

Kind regards

[cambrialas]

Does not compile on Windows, array length is not constant at compile time. Will fix tomorrow, live in GMT+1 zone.