Refactor for Swift 2
Refactor for Swift 2

* Make more extensive use of enums for Accessible and SecurityClass
  This wraps up the kSecXXX values much more nicely, and makes them
  more easily accessible through the provided enums

nvh/Locksmith,liuruxian/Locksmith,gfontenot/Locksmith,jwells47/Locksmith,augmify/Locksmith,gfontenot/Locksmith,jwells47/Locksmith,hermanolsson/Locksmith,liuruxian/Locksmith,jwells47/Locksmith,hermanolsson/Locksmith,vasco2ramos/Locksmith,carabina/Locksmith,jwells47/Locksmith,colemancda/Locksmith,gfontenot/Locksmith,nvh/Locksmith,KimBin/Locksmith,summerHearts/Locksmith,owenwuef/Locksmith,alessandrostone/Locksmith,pheld/Locksmith,vasco2ramos/Locksmith,carabina/Locksmith,hejunbinlan/Locksmith,owenwuef/Locksmith,tucali/Locksmith,owenwuef/Locksmith,pheld/Locksmith,hejunbinlan/Locksmith,KimBin/Locksmith,owenwuef/Locksmith,bestwpw/Locksmith,gfontenot/Locksmith,gfontenot/Locksmith,liuruxian/Locksmith,liuruxian/Locksmith,nvh/Locksmith,augmify/Locksmith,summerHearts/Locksmith,liuruxian/Locksmith,voidException/Locksmith,colemancda/Locksmith,augmify/Locksmith,alessandrostone/Locksmith,bestwpw/Locksmith,nvh/Locksmith,matthewpalmer/Locksmith,voidException/Locksmith,augmify/Locksmith,wimirwan/Locksmith,jwells47/Locksmith,owenwuef/Locksmith,tucali/Locksmith,matthewpalmer/Locksmith,nvh/Locksmith,augmify/Locksmith,wimirwan/Locksmith