Add MySQL plugin to Mac OS X

Added options:

  lin: -plugin-sql-mysql

Task-number: QTBUG-29802
Change-Id: I7e9d660004eec7706f58061756c020a3a56a867e
Reviewed-by: Iikka Eklund <iikka.eklund@digia.com>
Update installer graphics

Change-Id: Ie7e3718b0e082391e7979ca2f81863692b0cf2f7
Reviewed-by: Sergio Ahumada <sergio.ahumada@digia.com>
Reviewed-by: Iikka Eklund <iikka.eklund@digia.com>