* Resolve dir argument of getLocalNodeFiles function
The getLocalNodeFiles is called 3 times. Each time it called, the callee needs to resolve the dir argument.
That was not done for several of calls, and local modules (specified in the "nodesDir" setting) were not returned to client because of that.
This fix will allow to make sure the dir is consistently resolved.
* Several changes in "localfilesystem_spec.js":
- Changed checkNodes to verify that every node's file property is resolved, i.e. containst absolute path, not relative.
- Added a unit-test "Finds nodes in settings.nodesDir (string,relative path)"
* prevent registry.registerNodeConstructor from overriding a constructors protoype
* fix for node < v5.0.0
* exercise another code path
* altering __proto__ for node < v0.12
* move inheritance code to helper function
The tests still use it in places - particular localfilesystem tests,
but those tests need to be redone with sinon stubbing in place and
not rely on real fs operations.
