Unit testing in Ant; upgraded to ArcGIS Runtime 10.2.3; misc. improvements

A laundry list of improvements:
- Migrated to 10.2.3 (fixed #29)
- Moved location of unit tests (i.e. new location for VehicleCommanderJFrameTest.java)
- Running unit tests in Ant build file (build.xml) (fixed #28)
- Removed application build number, which is no longer relevant
- Not allowing invalid UDP port number for messaging
- Fixed threading issue by making `MapController.addLayer(int, Layer, boolean)` synchronized
- Improved window positioning. App window will open in location and state where it last closed, unless it was minimized or it would be off the current screen configuration (e.g. you ran it on monitor 2, disconnected monitor 2, and ran it again; in this case, it will display at 0,0 on the primary monitor).

This is most, but not all, of the work needed for the [10.2.3 release](https://github.com/Esri/vehicle-commander/milestones/Vehicle%20Commander%2010.2.3).