mandate security and privacy consideration section(s)

[samuelweiler]

resolving #131

[svgeesus]

LGTM

[svgeesus]

@ianbjacobs I like that wording, which would also resolve #144

[svgeesus]

Also fixed by #268 which is to resolve #144

[samuelweiler]

It's not clear to me that the template needs to go into detail about how editors organize those considerations into N sections.

For sec and privacy, I specifically want special sections. It's not clear to me that this needs to be in the charter - I'm fine stripping it out of the charter entirely. It's too verbose as it is.

Further, we want spec authors to do the consideration themselves - the section should not populated with review comments; it should be from the authors.

[samuelweiler]

Instead resolved via #300, though that still uses "should"