Split out properties into their own module.
Allows for improved maintainability & extensibility.
Updated file headers
Register Properties
Not sure if this is actually needed as object.py doesn't have one and is
registered correctly. Should look into it for general registration.
Added operators to add/remove items from the extra_data collection.
Expose the extra_data collection through a UIList in the object pane.
Removed manual registration of classes.
If each class is imported by the parent __init__ of a module then it
will automatically call the classmethod register for any classes that
are imported.
Created an extra data store.
Adds a Data holder property to manage the collection of extra data
objects.
Added Object ExtraData Panel with functioning UI List.
Added basic interface for adding by type and expose their data.
Removed vertex group panel as not currently used.
Fix bug on access of empty collection in draw method for extra_data
Testing adding property types, it no work so good. 
Commiting this to keep track of what I was implement, doesn't break
anything as I disconnected it but still worth persuing.
Removed log file
Format fixing
Fixed issue with UI registration
Removed commented out registers
Removed unneeded operator registration.
Updated attribute file for eof
Added extra line as it breaks the debugger
Merge pull request #192 from neomonkeus/feature/ui_partition_list

Properties split