API Management service updates

We made the following improvements to the Azure API Management service: * **JWT token policy**We added the _[match](https://msdn.microsoft.com/en-us/library/azure/034febe3-465f-4840-9fc6-c448ef520b0f#ValidateJWT)_ attribute to the _claim_ element to enable a degree of control over how claims in the policy are matched against those in the JWT token. * **Proxy server**The **Server** header is stripped from responses. * **Developer portal**The **Sign in** and **Sign up** menu items on the portal are hidden when no identity providers are selected. * **Developer portal**We made a few changes to improve the usability of the documentation and console: * Response headers and response body are shown together in a single control * Request URL is back * Request body example, when provided, is used to populate the request body control * Double-clicking in text areas selects all content to simplify copying * Buttons are added to reveal secret values in the request * API Management * Features * [ API Management](https://azure.microsoft.com/en-gb/products/api-management/)