Add a test case for saving entities with associations.
Add a test case for saving entities with associations.

Saving an entity should validate all the entities that are going to be
saved up front. This makes it easier to build interfaces where all the
errors are shown.

Refs #3600

jjj117/cakephp,cakephp/cakephp,Phillaf/cakephp,davidyell/cakephp,tenkoma/cakephp,dkarvounaris/cakephp,thinkingmedia/cakephp,HavokInspiration/cakephp,tisu2tisu/cakephp,burriko/cakephp,berrygoudswaard/cakephp,Phillaf/cakephp,cakephp-fr/cakephp,cakephp/cakephp,tgr0ss/cakephp,petteyg/cakephp,dkarvounaris/cakephp,berrygoudswaard/cakephp,michaelze/cakephp,adopico/cakephp,nrother/cakephp,ionas/cakephp,cakephp/cakephp,kumamidori/cakephp,tisu2tisu/cakephp,yinhe007/cakephp,thinkingmedia/cakephp,tgr0ss/cakephp,mvdriel/cakephp,jeffblack360/cakephp,ndm2/cakephp,garethellis36/cakephp,ndm2/cakephp,ADmad/cakephp,jerems02/cakephp,ADmad/cakephp,adopico/cakephp,CakeDC/cakephp,thinkingmedia/cakephp,eboominathan/cakephp,dakota/cakephp,eboominathan/cakephp,mvdriel/cakephp,garethellis36/cakephp,HavokInspiration/cakephp,erikfig/cakephp,davidyell/cakephp,CakeDC/cakephp,elboletaire/cakephp,pbaire/cakephp,eryw/cakephp,burriko/cakephp,timhoeppner/cakephp,jerems02/cakephp,bravo-kernel/cakephp,gmponos/cakephp,justinyost/cakephp,dakota/cakephp,CVO-Technologies/cakephp,justinyost/cakephp,dkarvounaris/cakephp,ADmad/cakephp,web-player/cakephp,CakeDC/cakephp,CVO-Technologies/cakephp,mvdriel/cakephp,eryw/cakephp,burriko/cakephp,nrother/cakephp,kumamidori/cakephp,davidyell/cakephp,HavokInspiration/cakephp,CakeDC/cakephp,ADmad/cakephp,elboletaire/cakephp,jerems02/cakephp,cakephp-fr/cakephp,bravo-kernel/cakephp,bravo-kernel/cakephp,Balachan27/cakephp,ndm2/cakephp,tisu2tisu/cakephp,garethellis36/cakephp,pbaire/cakephp,petteyg/cakephp,mvdriel/cakephp,Phillaf/cakephp,garethellis36/cakephp,berrygoudswaard/cakephp,yinhe007/cakephp,CVO-Technologies/cakephp,ionas/cakephp,nrother/cakephp,elboletaire/cakephp,khoimt/cakephp-study,jjj117/cakephp,cakephp/cakephp,michaelze/cakephp,khoimt/cakephp-study,tenkoma/cakephp,Balachan27/cakephp,akintoey/cakephp,tenkoma/cakephp,dakota/cakephp,eboominathan/cakephp,web-player/cakephp,jeffblack360/cakephp,justinyost/cakephp,timhoeppner/cakephp,petteyg/cakephp,jeffblack360/cakephp,jjj117/cakephp,kumamidori/cakephp,ndm2/cakephp,adopico/cakephp,gmponos/cakephp,dakota/cakephp,tgr0ss/cakephp,timhoeppner/cakephp,Balachan27/cakephp,tenkoma/cakephp,yinhe007/cakephp,petteyg/cakephp,pbaire/cakephp,erikfig/cakephp,ionas/cakephp,cakephp-fr/cakephp,akintoey/cakephp,khoimt/cakephp-study,web-player/cakephp,erikfig/cakephp,michaelze/cakephp,eryw/cakephp,akintoey/cakephp,gmponos/cakephp