rewrite all the model things

A first step in cleaning up the model code
default PumpObject __string__/__unicode__

also _striptags function for basic html to text functionality
Activity.__unicode__

Now prints stripped Activity.content
Collection.__unicode__
Comment.__unicode__
Feed.__unicode__
Image.__unicode__
Note.__unicode__
Person.__unicode__
Place.__unicode__

Place.name is now Place.display_name
fix Person.__repr__
Remove __repr__
change PumpObject.__unicode__

return display_name if there
ignore_attr

Don't check for ignore_attr in Mapper, remove them from obj._mapping
instead.
add 'liked' to ignore_attr
Set all attributes

Instead of skipping an object attribute which has no data to unserialize, we
now set it to None (or empty list for lists)
Add attributes to ignore