Invalidated document cache from FormPreserve.
Removed cached doc on form submit.
Prevented replacing ID of doc from cache.
Merged cache into existing doc. Removed unregister.
Created new object for context.doc
Merge branch 'master' of https://github.com/aldeed/meteor-autoform

# By Eric Dobbertin
# Via Eric Dobbertin
* 'master' of https://github.com/aldeed/meteor-autoform:
  update collection2 weak dependency to 2.0.0
Merge branch 'master' of https://github.com/aramk/meteor-autoform

* 'master' of https://github.com/aramk/meteor-autoform:
  Created new object for context.doc
Merge pull request #334 from aramk/master

FormPreserve fixes