This patch adds event handlers to RB.DialogView for submit and 

keydown. The form submit event handler fixes the bug where pressing

Enter on the upload file dialog (RB.UploadAttachmentView) would 

cancel the file upload instead of actually uploading it. Pressing the 

return key on RB.DialogView dialogs that have a completed form will 

now submit the form instead of reloading the page and discarding 

changes unless the form specifies an action explicitly. The keydown 

event handler allows the dialog to be closed when the Escape key

is pressed.
Since RB.DialogView is a child of the modalBox, it needs to listen 

to keydown events from the main box area and not from its own content 

area so that it can handle events from within it. This means we can't 

use the events map for the keydown event and have to bind an explicit 

keydown event handler on .modalbox-inner.

New unit tests:

- triggering submit with primary button enabled triggers the button

- triggering submit with primary button disabled on a dialog does 

nothing

- triggering submit with primary button enabled on a dialog with a 

form does nothing

- triggering keydown using the Escape key hides the dialog
Manual testing:
File upload dialog:

- pressing Enter after opening the dialog and not filling out any 

fields does nothing

- pressing Enter after uploading a file & editing the caption uploads 

the file with the caption

- pressing Escape after opening the dialog hides the dialog
New review request dialog:

- pressing Escape after opening the dialog hides the dialog