Fix catch for exporting a parented mesh with no armature modifier
applied. submitted by misternad in irc
Merge pull request #171 from Ghostwalker71/fix/modifier_catch

Fix catch for exporting a parented mesh with no armature modifier
Fix for the dismember check also removed bad register in the init.
Merge pull request #173 from Ghostwalker71/fix/broken_link

Fix for the dismember check also removed bad register in the init.
Cleaner fix for the ungrouped vertices block. plus a todo off the list
as well.
Merge pull request #174 from Ghostwalker71/fix/broken_link

Cleaner fix for the ungrouped vertices block. plus a todo off the list
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.