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 alloc] init];
NSString* mailto = defaults.SMTPto;
defaults.SMTPTo = @"newuser";
```

it also creates easy access to autopkg's defaults  and let's 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.
```
[LGDefaults standardUserDefaults] objectForKey:@"MYNEWKEY"]
```