Auto-create appropriate scheduled runs on creation (#170)

* auto create extension run on extension creation

* fix formatting

* fix

* datastructs

* ?

* prevent extensions from crashing

* add print

* get run config at ext creation time

* add warning

* also create the scheduled run for a new assignment

* store default run ID in the assignment

* try this

* fix

* load the final grading run config when creating an extension

* require grading time config to create an assignment

* help

* icon

* update words

* support

* help

* save start

* hold defaults

* Revert "hold defaults"

This reverts commit f536823.

* test

* fix

* help

* reorder

* default to

* ?

* Revert "?"

This reverts commit 3ef6f83.

* help

* help

* delete extension run when deleting an extension

* fix

* fix 3

* reload on closing extensions page

* use jquery

* fix

* fix 3?

* sigh

* remove print statements