Added orbital camera around current node with the middle mouse button.
The post render update is skipped while orbiting.
Merge branch 'orbit_camera_patch' into req_orbit_camera
Hide also the gizmo when orbiting.
Prevent unnecessary generation of Urho3D.h. Closes #98.

Also attempt to fix the project created by cmake-gui using non-standard build directory to find the generated Urho3D.h file.
Add new MessageBox class for showing short messages in a modal window.

Also:
- Enhance Editor to show error message box when saving action fails.
- Cleanup DefaultStyle.xml and at the same time create more common styles for reuse.
- Remove unused member variable in FileSelector class.
- ListView class does not assume vertical layout of its items. In theory we could have horizontal layout items if it is being styled as such.
- Prevent UIElement XML serialization to save invalid "UIElement" style to the final output. Fix invalid style (if already exist in the loaded UI layout) to cause error in attribute filtering when serializing.
Travis CI: API documentation update at 2014-01-01 10:34:53 UTC.
[ci skip]
Merge remote-tracking branch 'upstream/master'
Merge branch 'master' of /home/user/git/barrettcolin-Urho3D.git.bare