add button to change lineedit value with mouse drag. Inspired from Unreal editor.
set style for drag slider
fixed coding style
prevent save undo action while drag in material
Change icon for drag slider
Merge remote-tracking branch 'remotes/rifai/master'
Merge branch 'master' of https://github.com/urho3d/Urho3D
If DirectX SDK is not searched for or not found, DIRECT3D_LIBRARIES is not defined. Use hardcoded library names in that case. Closes #504.
For Travis CI - switch CI build to use Raspberry-Pi build environment.