Nile updated !!!

[SPG]

Two more updates :-

- version 0.56
Fixed problem with marking valid expressions as invalid.
Fixed problem where Save As… was not changing the target file name.
Fixed problem with canceling action creation.
Added distance measurement tool.
Fixed item selection in events action list.

- version 0.55
Fixed some GUI display issues in tab controls.
Fixed deleting of waypoint lists.
Made first pass at WAC command definition file.
Fixed deleting events.
Modified if/then dialog boxes, made them much larger.
Fixed deleting objects and their effect on waypoint lists and events.
Added color coding to indicate broken expressions in the event editor.