CS2146 fixes

fixes for submission UI. there are two to-dos with regard to API calls for deliverable update and delete.

## deliverable update

following message is returned while trying to call *PUT* request

code is at: https://github.com/soe/cs-website-cms/blob/cs2146-fix/app/models/submission.rb#L125

```
{"success":false,"message":"METHOD_NOT_ALLOWED: HTTP Method 'PATCH' not allowed. Allowed are HEAD,GET,POST"}
```
## deliverable delete

code is at: https://github.com/soe/cs-website-cms/blob/cs2146-fix/app/models/submission.rb#L143

please let me know request to be made for *DELETE* request