Created the Cloud Data tutorial in Swift

"where" is a keyword in Swift and you can not use it in context to AGSQuery without using the back ticks.

To use a reserved word as an identifier, put a back tick (\`) before and after it. For example, class is not a valid identifier, but \`class\` is valid. The backticks are not considered part of the identifier;  \`x\` and x have the same meaning. https://developer.apple.com/library/prerelease/ios/documentation/Swift/Conceptual/Swift_Programming_Language/LexicalStructure.html#//apple_ref/doc/uid/TP40014097-CH30-XID_878