refact: use DoricSingleton to hold all static or singleton objects

doric-iOS/Example/Example/AppDelegate.m

@@ -9,7 +9,7 @@
 #import "AppDelegate.h"
 #import "NavigationController.h"
 #import "ViewController.h"
-#import "DoricRegistry.h"
+#import <DoricCore/Doric.h>
 
 #if __has_include(<SDWebImage/SDWebImage.h>)
 
@@ -27,7 +27,7 @@ @implementation AppDelegate
 
 
 - (void)localeChanged {
-    [DoricRegistry setEnvironmentValue:@{
+    [Doric setEnvironmentValue:@{
             @"localeLanguage": [[NSLocale autoupdatingCurrentLocale] objectForKey:NSLocaleLanguageCode],
             @"localeCountry": [[NSLocale autoupdatingCurrentLocale] objectForKey:NSLocaleCountryCode],
     }];

doric-iOS/Example/Example/ViewController.m

@@ -46,9 +46,9 @@ - (void)viewDidLoad {
         it.dataSource = self;
         it.delegate = self;
     }]];
-    [DoricRegistry register:[DemoLibrary new]];
-    [DoricRegistry enablePerformance:YES];
-    [DoricRegistry enableRenderSnapshot:YES];
+    [Doric registerLibrary:[DemoLibrary new]];
+    [Doric enablePerformance:YES];
+    [Doric enableRenderSnapshot:YES];
 }
 
 - (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {