Fixed: CPDateFormatter getObjectValue: with nil errorDescription crash.

Like for all formatters, a nil errorDescription just means we don't care about the error description if there is an error.

Fixes #2030.
Fixed: CPDateFormatter stringFromDate:"" did not return a default date.

In Cocoa formatting an empty string actually results in a particular date. For consistency we should handle an empty string the same way.

Refs #2030.
New: make bootstrap.sh use Github with SSL.

This is the default for Github now and accessing the old bare http URL just causes a redirect to https.
Test: don't run Travis setup quietly to make it easier to track setup errors.