Add "integration.autorebuild" configuration variable

This causes the integration branch to be rebuild after it has been
created/edited without the user needing to specify --rebuild.

Signed-off-by: John Keeping <john@keeping.me.uk>
Add --no-rebuild option

This allows the user to suppress the behaviour of the
'integration.autorebuild' configuration variable.

Signed-off-by: John Keeping <john@keeping.me.uk>
Reformat option specification

Purely a whitespace change.

Signed-off-by: John Keeping <john@keeping.me.uk>