New additions to AutoUV menus

[Micheus]

It was added some missing options to the context menu in AutoUV as well as an option to
tile the texture which can be useful for some projects (like for games).

NOTE:
New options added to AutoUV:

• Added the options Center, Center X and Center Y to the Align command;
• Added the RMB option to Scale command to choose a reference point;
• Added the RMB option to Rotate command to choose a reference point;
• Added option to show the background texture in tiled mode.