MacDeployQt: Add -always-overwrite option.

Support incrementally re-deploying to an existing app
bundle. Overwrite files that already exist in the
bundle. Disable the "Can not find Qt" warning. Skip
plugin deployment if Qt can not be found.

Remove usages of the Qt4-style binary packages from
/Developer.

Task-number: QTBUG-36043
Change-Id: I11d1e36e6beef24b55979fc4d853e19b60551740
Reviewed-by: Gabriel de Dietrich <gabriel.dedietrich@digia.com>