Commented Feature: Allow DbContext to be created with an already-open existing connection plus ensure connection closing is consistent with opening [45]

This item was migrated from the DevDiv work item tracking system [ID=7992]. <br />
Comments: See also http://vstfdevdiv:8080/DevDiv2/DevDiv/_workitems#_a=edit&id=240698 which describes a situation where a user took manual control of the connection but had it prematurely closed for him by EntityConnection code.