README consolidation and link fixes (Azure#4890)

* Add Samples section. Remove en-us from links.

* Remove en-us.

* Fix samples links in storage.

* Move samples to correct location.

* Fix broken links in README. Correct formatting.

* remove [package] from README because none of the others have it.

* Add syntax highlighting alias java to snippets.

* Undo * in appconfig

* Update shared key credential steps.

* Updating README with comments.

sdk/keyvault/azure-keyvault-keys/README.md

@@ -292,8 +292,8 @@ keyAsyncClient.getKey("keyName").subscribe(keyResponse -> {
 
 Delete an existing Key by calling `deleteKey`.
 ```java
-keyAsyncClient.deleteKey("keyName").subscribe(deletedKey ->
-   System.out.printf("Deleted Key's deletion time %s \n", deletedKey.deletedDate().toString()));
+keyAsyncClient.deleteKey("keyName").subscribe(deletedKeyResponse ->
+   System.out.printf("Deleted Key's deletion time %s \n", deletedKeyResponse.value().deletedDate().toString()));
 ```
 
 ### List Keys Asynchronously