Add Lua Script API document.

git-svn-id: http://urho3d.googlecode.com/svn/trunk@2557 3bd170d8-ddcf-f82c-f583-7a401ccf5608
Refactored slider page event parameters to be simpler and fixed unintended scrolling while hovering without mouse button pressed.
Change CheckBox to react to click begin (as it was before) so that ListView hierarchy toggling doesn't break.


git-svn-id: http://urho3d.googlecode.com/svn/trunk@2558 3bd170d8-ddcf-f82c-f583-7a401ccf5608