Add setting for auto-send and auto-delete

[lognaturel]

orx:auto-send and orx:auto-delete were added as attributes to the submission element in getodk/xforms-spec#100. Both can be set to either "true" or "false" and can combine. For example:
<submission orx:auto-delete="true" orx:auto-send="false">

It seems that to fit existing XLSForms idioms, each would get its own settings column.

[lognaturel]

If I could get a sanity check on how it should be represented in XLSForm I'd be happy to take a stab at this.

[MartijnR]

each would get its own settings column

Makes sense!