Bump to 2.0 RC 2 dev.
Don't check for the static/ext/ directory in DEBUG mode.

When running in DEBUG mode, the manual update checks were checking for
htdocs/static/ext/, but adding this would cause problems, since we don't
want a htdocs/static/ in a dev install.

We now only make this check if not running in DEBUG mode.

Reviewed at https://reviews.reviewboard.org/r/5668/