disabled if none, added show popup indicator
Prevent message box crashes due to corrupted or missing data dir.

Delay factories debug tests after all the subsystems and resource paths are added.
Register MessageBox object factory.
Fix build using Urho3D as external library. Closes 112.

Add test cases in Travis CI to test build using Urho3D as external library in external (non Urho3D) project.
For Travis CI - explicitly request for bash shell to keep Ubuntu happy.
Added Development Base. This sets Debug Information for Debug Builds to /C7 and none on Release Builds. Modifies the install settings and ignore flag as well.
Modified Sound to provide its own unique category for UI sounds