part of the problem with the original `-destination` implementation... was that it only supported a single destination.

e.g., the following is a valid invocation of xcodebuild ...

```
xcodebuild -project TestWhat.xcodeproj -scheme TestWhat -sdk iphonesimulator test \
  -destination 'name=iPhone Retina (3.5-inch),OS=6.1' \
  -destination 'name=iPhone Retina (3.5-inch),OS=7.0'
```

And, this is why in my branch... I was moving in the direction of having destination information encapsulated in a _DestinationInfo_ object:
https://github.com/facebook/xctool/commit/0e2d84df0e329c864666fa7fa27b58c75dab5a20#diff-785a8bc86a4715de23cf35cf6644da65R19

The ultimate goal was to eventually change ...

```objc
@property (nonatomic, copy) NSString *destination;
```

to hold multiple destinations ...

```objc
@property (nonatomic, copy) NSArray *destinations;
```