Stub out of LGDefaults class, complete with setters/getters

This is a subclass of NSUserDefaults complete with accessors.

so instead of doing this 
```Objective-c
NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults]
NSString* mailto = [defaults objectForKey:@"SMTPTo"];
[defaults setObject:@"newuser" ForKey:@"SMTPTo"];

```
now you can do this
```Objective-c
LGDefaults *defaults = [LGDefaults new];
NSString* mailto = defaults.SMTPto;
defaults.SMTPTo = @"newuser";
```

it also creates easy access to autopkg's defaults to give us the ability let autopkgr modify those
```Objective-c
@property (copy, nonatomic) NSString *autoPkgCacheDir;
@property (copy, nonatomic) NSString *munkiRepo;
@property (copy, nonatomic,readonly) NSString *autoPkgRecipeRepoDir;
@property (copy, nonatomic,readonly) NSArray *autoPkgRecipeSearchDirs;
@property (copy, nonatomic,readonly) NSDictionary *autoPkgRecipeRepos;
```

since it is a subclass you can use it just as you would NSUserDefaults in the case
there are specialized keys you need to set.

I've modified LGAppDelegate in the initial commit to use this class and if you like the look I could start applying it to some of the other code.