Make ManageMyGrants look more like /authorize

* Instead of radio buttons to select "update" or "revoke", use two
  separate buttons.
* Rearrange fields to match the order on /authorize
* Make description text rather than a read-only form field
* Remove "consumer key" field

Bug: 53964
Change-Id: Ifea6f6195a959444ca69c3ea30215d4169fad950
Merge "Make ManageMyGrants look more like /authorize"