Release 0.7.4 Cleanup & Image support

[Manfred Moitzi]

• NEW: support for DXF entity IMAGE (work in progress)
  
• NEW: preserve leading file comments (tag code 999)
  
• NEW: writes saving and upgrading comments when saving DXF files; avoid this behavior by setting options.store_comments = False
  
• NEW: ezdxf.new() accepts the AutoCAD release name as DXF version string e.g. ezdxf.new(‘R12’) or R2000, R2004, R2007, …
  
• NEW: integrated acadctb.py module from my dxfwrite package to read/write AutoCAD .ctb config files; no docs so far
  
• CHANGE: renamed Drawing.groups.add() to new() for consistent name schema for adding new items to tables (public interface)
  
• CHANGE: renamed Drawing.<tablename>.create() to new() for consistent name schema for adding new items to tables, this applies to all tables: layers, styles, dimstyles, appids, views, viewports, ucs, block_records. (public interface)
  
• CHANGE: renamed Layouts.create() to new() for consistent name schema for adding new items to tables (internal interface)
  
• CHANGE: renamed Drawing.create_layout() to new_layout() for consistent name schema for adding new items (public interface)
  
• CHANGE: renamed factory method <layout>.3Dface() to 3dface()
  
• REMOVED: logging and debugging options
  
• BUGFIX: fixed attribute definition for align_point in DXF entity ATTRIB (AC1015 and newer)
  
• Cleanup DXF template files AC1015 - AC1027, file size goes down from >60kb to ~20kb