Use AdminObjectEdit for all edit pages.

This requires https://github.com/silverorange/admin/pull/16
Update AdminComponent and AdminSubComponent to use loadByShortname().

I've left the deprecated loadFromShortname(), but since we have so few places to update it, we should kill it in the near future.
Code cleanup and class map everything.

Might as well clean up the files while I have them open.
Use the more verbose admin_component for the variable name.

This is becauscomponent is already defined by the parent class AdminPage for other uses.
Update to use new getObjectPropertyWidgetMapping() method.

Requires https://github.com/silverorange/admin/pull/18
Reflect method name change in Admin.
s/getObjectPropertyWidgetMapping/getObjectUiValueNames
don't translate exception messages.
Fix shortname validation logic.
Merge pull request #17 from isaacgrant/use-admin-object-edit

Use AdminObjectEdit for all admin component edit pages