rework on graphics.cpp, implement some GFX with lua

modules/gfx/gfx.lua

@@ -0,0 +1,26 @@
+GFX = { }
+
+function GFX.fadeIn(widget, time, elapsed)
+    if not elapsed then elapsed = 0 end
+    if not time then time = 750 end
+    widget.opacity = math.min((255*elapsed)/time, 255)
+    if elapsed < time then
+        scheduleEvent(function()
+                        GFX.fadeIn(widget, time, elapsed + 30)
+                      end, 30)
+    end
+end
+
+function GFX.fadeOut(widget, time, elapsed)
+    if not elapsed then elapsed = 0 end
+    if not time then time = 750 end
+    widget.opacity = (255*(time - elapsed))/time
+    if elapsed < time then
+        scheduleEvent(function()
+                        GFX.fadeOut(widget, time, elapsed + 30)
+                      end, 30)
+    else
+        widget:destroy()
+    end
+end
+

modules/gfx/gfx.otmod

@@ -0,0 +1,15 @@
+Module
+  name: gfx
+  description: Contains utilities for generating graphics effects
+  author: OTClient team
+  website: https://github.com/edubart/otclient
+  version: 0.2
+  autoLoad: true
+  dependencies:
+    - core
+
+  onLoad: |
+    require 'gfx'
+    return true
+
+