Fix minor Orderer bug in Perseus One edit tab.

Currently if you drag cards into the Orderer from the bank, they persist
when you start editing a different item in Perseus One. The underlying
cause is that the Orderer, like many of our draggy widgets, relies on
state instead of props for its core functionality.

Test Plan:
Reproduce bug on local webapp before change.
Fail to reproduce bug on local webapp after change.

Auditors: jack