refs #9 add UCMainContent
This class contain drawing pane. This is just for setting it up. Inserting inscroll pane. TODO: Add drawing listeners to drawing pane.
refs #9 rename UCMainContent to UCMainContentController
Also fix dragging object on screen.
refs #9 change UCMainContePane to UCMainContent
Change it in UCMainContentController, that way data are separated from methods that control behavior about them.